ATLANTIC RICHFIELD CO /DE
SC 14D1, 1995-08-25
PETROLEUM REFINING
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<PAGE>
 
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                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549
 
                                SCHEDULE 14D-1
 
TENDER OFFER STATEMENT PURSUANT TO SECTION 14(d)(1) OF THE SECURITIES EXCHANGE
                                  ACT OF 1934
 
                                ARAN ENERGY PLC
                           (NAME OF SUBJECT COMPANY)
 
                           ARCO IRISH HOLDINGS INC.
 
                          ATLANTIC RICHFIELD COMPANY
                                   (BIDDER)
 
                       ORDINARY SHARES OF IR20P EACH AND
       AMERICAN DEPOSITARY SHARES, EACH REPRESENTING 30 ORDINARY SHARES
                        (TITLE OF CLASS OF SECURITIES)
 
                                  038-528-105
                     (CUSIP NUMBER OF CLASS OF SECURITIES)
 
                                 DIANE A. WARD
                          ATLANTIC RICHFIELD COMPANY
                            515 SOUTH FLOWER STREET
                         LOS ANGELES, CALIFORNIA 90071
                                (213) 486-2808
 (NAME, ADDRESS AND TELEPHONE NUMBERS OF PERSON AUTHORIZED TO RECEIVE NOTICES
                    AND COMMUNICATIONS ON BEHALF OF BIDDER)
                           CALCULATION OF FILING FEE
 
TRANSACTION VALUATION*                           AMOUNT OF FILING FEE
----------------------                           --------------------
    $260,300,000                                         $52,060
 
*   For purposes of calculating the filing fee pursuant to Regulation (S)240.0-
    11(d), the transaction valuation is based upon the purchase of 261,591,729
    Ordinary Shares of IR20p each (including Ordinary Shares represented by
    American Depositary Shares) plus, assuming the exercise of outstanding
    options, an additional 12,408,271 Ordinary Shares at IR60p per share for
    cash and the multiplication of such aggregate purchase price by the currency
    exchange rate of IR(Pounds)1 = US$1.577 (such currency exchange rate being
    derived from the Financial Times dated August 24, 1995).
 
[_] Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
    and identify the filing with which the offsetting fee was previously paid.
    Identify the previous filing by registration statement number, or the form
    or schedule and the date of its filing.
 
Amount Previously Paid:        Not Applicable
Form or Registration No.:      Not Applicable
Filing Party:                  Not Applicable
Dated Filed:                   Not Applicable
 
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<PAGE>
 
CUSIP No. 038-528-105
<TABLE>
  <C> <S>
  1)  Name of Reporting Person, S.S. or I.R.S. Identification No. of Above
      Person
      ARCO Irish Holdings Inc.
      -----------------------------------------------------------------------
-----------------------------------------------------------------------------
  2)  Check the Appropriate Box if a Member of a Group (See Instructions)
      [_] (a) 
              ---------------------------------------------------------------
      [_] (b) 
              ---------------------------------------------------------------
 
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  3)  SEC Use Only 
                  -----------------------------------------------------------

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  4)  Sources of Funds (See Instructions) AF
                                          -----------------------------------

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  5)  [_] Check if Disclosure of Legal Proceedings is Required Pursuant to
      Items 2(e) or 2(f)
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  6)  Citizenship or Place of Organization Delaware
                                           ----------------------------------
-----------------------------------------------------------------------------
  7)  Aggregate Amount Beneficially Owned by Each Reporting Person 0
                                                                   ----------
-----------------------------------------------------------------------------
  8)  [_] Check if the Aggregate Amount in Row 7 Excludes Certain Shares (See
      Instructions)
-----------------------------------------------------------------------------
  9)  Percent of Class Represented by Amount in Row 7 0
                                                      -----------------------
-----------------------------------------------------------------------------
  10) Type of Reporting Person (See Instructions) CO
                                                  ---------------------------
-----------------------------------------------------------------------------
</TABLE>
<PAGE>
 
CUSIP No. 038-528-105
<TABLE>
  <C> <S>
  1)  Name of Reporting Person, S.S. or I.R.S. Identification No. of Above
      Person
      Atlantic Richfield Company
      -----------------------------------------------------------------------
-----------------------------------------------------------------------------
  2)  Check the Appropriate Box if a Member of a Group (See Instructions)
      [_] (a) 
              ---------------------------------------------------------------
      [_] (b) 
              ---------------------------------------------------------------
-----------------------------------------------------------------------------
  3)  SEC Use Only 
                   ----------------------------------------------------------

-----------------------------------------------------------------------------
  4)  Sources of Funds (See Instructions) WC
                                          -----------------------------------
-----------------------------------------------------------------------------
  5)  [_] Check if Disclosure of Legal Proceedings is Required Pursuant to
      Items 2(e) or 2(f)
-----------------------------------------------------------------------------
  6)  Citizenship or Place of Organization Delaware
                                           ----------------------------------
-----------------------------------------------------------------------------
  7)  Aggregate Amount Beneficially Owned by Each Reporting Person 0
                                                                   ----------
-----------------------------------------------------------------------------
  8)  [_] Check if the Aggregate Amount in Row 7 Excludes Certain Shares (See
      Instructions)
-----------------------------------------------------------------------------
  9)  Percent of Class Represented by Amount in Row 7 0
                                                      -----------------------
-----------------------------------------------------------------------------
  10) Type of Reporting Person (See Instructions) CO
                                                  ---------------------------
-----------------------------------------------------------------------------
</TABLE>
<PAGE>
 
ITEM 1. SECURITY AND SUBJECT COMPANY.
 
  (a) The name of the subject company is Aran Energy plc ("Aran"). The address
of Aran's principal executive office is: Elm House, Clanwilliam Court, Lower
Mount Street, Dublin 2, Ireland.
 
  (b) This Statement relates to the offer (the "Offer") by ARCO Irish Holdings
Inc., a Delaware corporation ("ARCO Irish Holdings") and an indirect wholly
owned subsidiary of Atlantic Richfield Company, a Delaware corporation
("ARCO"), to purchase all of the outstanding (a) ordinary shares of
IR(Pounds)0.20 each ("Ordinary Shares") of Aran and (b) American Depositary
Shares ("ADSs") of Aran each representing thirty Ordinary Shares. The Ordinary
Shares and ADSs are collectively referred to herein as the "Aran Shares". The
Offer is subject to the terms and conditions set forth in the offer document
dated August 25, 1995 (the "Offer Document") (a copy of which is filed as
Exhibit (a)(1) hereto) and the related Letter of Transmittal for the ADSs (a
copy of which is filed as Exhibit (a)(2) hereto) and Form of Acceptance,
Authority and Election for the Ordinary Shares (a copy of which is filed as
Exhibit (a)(3) hereto). Information concerning the number of outstanding
Ordinary Shares and ADSs is set forth under the caption "Bases of Calculation
and Sources of Information" in Appendix 4 to the Offer Document and is
incorporated herein by reference. Information concerning the consideration
being offered therefor is set forth under the caption "The Offer" in the Offer
Document.
 
  (c) The information set forth under the caption "Market Price Data and
Principal Purchases" in Appendix 4 to the Offer Document is incorporated
herein by reference.
 
ITEM 2. IDENTITY AND BACKGROUND.
 
  (a)-(d) and (g). This Statement is filed by ARCO and ARCO Irish Holdings.
Information concerning the principal business, the address of the principal
offices and place of organization of each of ARCO and ARCO Irish Holdings is
set forth under the caption "Principal Office" in Appendix 2 to the Offer
Document and is incorporated herein by reference. Information concerning the
name, business address, present principal occupation or employment and
citizenship of each director and executive officer of ARCO as well as
information concerning the material occupations, positions, offices or
employments during the last five years of the directors and executive officers
of ARCO is set forth under the captions "Directors and Executive Officers of
ARCO" in Appendix 2 to the Offer Document and is incorporated herein by
reference. Information concerning the name, business address, present
principal occupation or employment and citizenship of each director and
executive officer of ARCO Irish Holdings as well as information concerning the
material occupations, positions, offices or employments during the last five
years of the directors and executive officers of ARCO Irish Holdings is set
forth under the captions "Directors and Executive Officers of ARCO Irish
Holdings" in Appendix 2 to the Offer Document and is incorporated herein by
reference.
 
  (e) and (f). During the last five years, neither ARCO nor ARCO Irish
Holdings, nor any person listed in Appendix 2 to the Offer Document under the
captions "Directors and Executive Officers of ARCO" and "Directors and
Executive Officers of ARCO Irish Holdings" has been either (i) convicted in a
criminal proceeding (excluding traffic violations or similar misdemeanors), or
(ii) a party to a civil proceeding of a judicial or administrative body of
competent jurisdiction and as a result of such proceeding was or is subject to
a judgment, decree or final order enjoining future violations of, or
prohibiting activities subject to, federal or state securities laws or finding
any violation of such law.
 
ITEM 3. PAST CONTRACTS, TRANSACTIONS OR NEGOTIATIONS WITH THE SUBJECT COMPANY.
 
  (a) The information set forth under "ARCO's Reasons for the Offer and Plans
for Aran" in Appendix 4 to the Offer Document is incorporated herein by
reference.
 
  (b) The information set forth under the caption "Background to the Offer" in
Appendix 4 to the Offer Document is incorporated herein by reference.
 
                                       1
<PAGE>
 
ITEM 4. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.
 
  (a)-(c). The information set forth under the caption "Amount and Source of
Funds" in Appendix 4 to the Offer Document is incorporated herein by
reference.
 
ITEM 5. PURPOSE OF THE TENDER OFFER AND PLANS OR PROPOSALS OF THE BIDDER.
 
  (a)-(g). The information set forth under the captions "ARCO's Reasons for
the Offer and Plans for Aran" and "Compulsory Acquisition" in Appendix 4 to
the Offer Document is incorporated herein by reference.
 
ITEM 6. INTEREST IN SECURITIES OF THE SUBJECT COMPANY.
 
  (a) and (b). The information set forth under the caption "Disclosure of
Interests and Dealings in Aran Shares" in Appendix 4 to the Offer Document is
incorporated herein by reference.
 
ITEM 7. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
TO THE SUBJECT COMPANY'S SECURITIES.
 
  The information set forth under the caption "Rule 10b-13 Exemption" in the
Offer Document as well as the information set forth under the captions
"Background to the Offer", "Disclosure of Interests and Dealings in Aran
Shares" and "Market Price Data and Principal Purchases" in Appendix 4 to the
Offer Document is incorporated herein by reference.
 
ITEM 8. PERSONS RETAINED, EMPLOYED OR TO BE COMPENSATED.
 
  The information set forth under the caption "Fees and Expenses" in Appendix
4 to the Offer Document is incorporated herein by reference.
 
ITEM 9. FINANCIAL STATEMENTS OF CERTAIN BIDDERS.
 
  The information set forth under the caption "Financial Statements" in
Appendix 2 to the Offer Document is incorporated herein by reference. The
incorporation by reference herein of such information does not constitute an
admission that such information is material to a decision by a security holder
of Aran whether to sell, tender or hold the Aran Shares being sought in the
Offer.
 
ITEM 10. ADDITIONAL INFORMATION.
 
  (a) and (e). Not applicable.
 
  (b)-(c) The information set forth under the caption "Legal and Regulatory
Matters" in Appendix 4 to the Offer Document is incorporated herein by
reference.
 
  (d) The information set forth under the caption "Certain Consequences of the
Offer--Margin Securities" in Appendix 4 to the Offer Document is incorporated
herein by reference.
 
  (f) Incorporated by reference herein is the information set forth in the
Offer Document, the Form of Letter of Transmittal, the Form of the Form of
Acceptance, Authority and Election for the Ordinary Shares, the Form of Notice
of Guaranteed Delivery, the press release dated August 21, 1995 and the press
release dated August 25, 1995 which are attached hereto as Exhibits (a)(1)
through (a)(4), (a)(10) and (a)(12), respectively.
 
                                       2
<PAGE>
 
ITEM 11. MATERIAL TO BE FILED AS EXHIBITS.
 
<TABLE>
   <C>     <S>
   (a)(1)  Offer Document dated August 25, 1995
   (a)(2)  Form of Letter of Transmittal
   (a)(3)  Form of the Form of Acceptance, Authority and Election for the
           Ordinary Shares
   (a)(4)  Form of Notice of Guaranteed Delivery
   (a)(5)  Form of Letter to Brokers, Dealers, Commercial Banks, Trust
           Companies and Other Nominees from Rothschild Inc.
   (a)(6)  Form of Letter to holders of Ordinary Shares from Rothschild Inc.
   (a)(7)  Form of Letter to holders of ADSs from Rothschild Inc.
   (a)(8)  Form of Letter to Clients from Brokers, Dealers, Commercial Banks,
           Trust Companies and Other Nominees
   (a)(9)  Guidelines for Certification of Taxpayer Identification Number on
           Substitute Form W-9
   (a)(10) Text of press release dated August 21, 1995
   (a)(11) Text of slide projection displays for presentations to institutional
           investors
   (a)(12) Text of press release dated August 25, 1995
   (a)(13) Summary advertisement dated August 25, 1995
   (a)(14) Newspaper advertisement dated August 25, 1995
   (a)(15) Substitute Form W-9
   (b)     Not applicable
   (c)     Not applicable
   (d)     Not applicable
   (e)     Not applicable
   (f)(1)  Text of slide projection displays for presentations to institutional
           investors (filed as Exhibit (a)(11) to this statement)
</TABLE>
 
                                       3
<PAGE>
 
  After due inquiry and to the best of its knowledge and belief, each of the
undersigned certifies that the information set forth in this statement is true,
complete and correct.
 
Date: August 25, 1995                     Atlantic Richfield Company
 
                                                    /s/ Terry G. Dallas
                                          By___________________________________
                                                Vice President & Treasurer
 
                                          ARCO Irish Holdings Inc.
 
                                                    /s/ Terry G. Dallas
                                          By___________________________________
                                                   Senior Vice President
 
                                       4
<PAGE>
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
 EXHIBIT NUMBER                     DESCRIPTION OF DOCUMENT
 --------------                     -----------------------
 <C>            <S>
    (a)(1)      Offer Document dated August 25, 1995
    (a)(2)      Form of Letter of Transmittal
    (a)(3)      Form of the Form of Acceptance, Authority and Election for the
                Ordinary Shares
    (a)(4)      Form of Notice of Guaranteed Delivery
    (a)(5)      Form of Letter to Brokers, Dealers, Commercial Banks, Trust
                Companies and Other Nominees
    (a)(6)      Form of Letter to holders of Ordinary Shares from Rothschild
    (a)(7)      Form of Letter to holders of ADSs from Rothschild
    (a)(8)      Form of Letter to Clients from Brokers, Dealers, Commercial
                Banks, Trust Companies and Other Nominees from Rothschild
    (a)(9)      Guidelines for Certification of Taxpayer Identification Number
                of Substitute Form W-9
    (a)(10)     Text of press release dated August 21, 1995
    (a)(11)     Text of slide projection displays for presentations to
                institutional investors
    (a)(12)     Text of press release dated August 25, 1995
    (a)(13)     Summary advertisement dated August 25, 1995
    (a)(14)     Newspaper advertisement dated August 25, 1995
    (a)(15)     Substitute Form W-9
    (b)         Not applicable
    (c)         Not applicable
    (d)         Not applicable
    (e)         Not applicable
    (f)(1)      Text of slide projection displays for presentations to
                institutional investors (filed as Exhibit (a)(11) to this
                statement)
</TABLE>

<PAGE>

                                                                EXHIBIT 99(a)(1)
 
ARCO IRISH HOLDINGS [LOGO]
 
                                 Cash Offer for
                                 Aran Energy plc
<PAGE>
 
                        The Generous Value of the Offer
 
 
 
                              [ART APPEARS HERE]

CHART DEPICTING THE PRICE MOVEMENT OF THE STOCK IN IR PENCE BEGINNING AUGUST
1991 AND CONTINUING THROUGH AUGUST 1995. IN ADDITION THE GRAPH REFLECTS THE 
4 YEAR HIGH (IR47p) AND THE PRICE BEFORE OFFER (IR42.5p) AND OFFER PRICE 
(IR60p).
 



 
 
No person has been authorised to give any information or to make any
representation on behalf of ARCO or ARCO Irish Holdings not contained in this
document or in the Acceptance Forms and, if given or made, any such information
or representation must not be relied upon as having been authorised. Neither
the delivery of this document and the Acceptance Forms nor any purchase
pursuant to the Offer shall, under any circumstances, create any implication
that there has been no change in the affairs of ARCO or ARCO Irish Holdings or
Aran since the date as of which information is furnished or the date of this
document.
<PAGE>
 
OFFER TO PURCHASE DATED 25 AUGUST 1995
 
THIS DOCUMENT IS IMPORTANT AND REQUIRES YOUR IMMEDIATE ATTENTION.
IF YOU ARE IN DOUBT ABOUT THIS OFFER YOU SHOULD CONSULT AN INDEPENDENT
FINANCIAL ADVISER WHO, IN THE CASE OF UK SHAREHOLDERS, IS AUTHORISED UNDER THE
FINANCIAL SERVICES ACT 1986.
 
IF YOU HAVE SOLD OR OTHERWISE TRANSFERRED ALL YOUR ARAN SHARES OR ARAN ADSs,
PLEASE PASS THIS DOCUMENT, TOGETHER WITH THE ACCOMPANYING ACCEPTANCE FORMS AND
(WHERE PROVIDED) THE REPLY-PAID ENVELOPE, AS SOON AS POSSIBLE TO THE PURCHASER
OR TRANSFEREE, OR TO THE BANK, STOCKBROKER OR OTHER AGENT THROUGH WHOM THE
SALE OR TRANSFER WAS EFFECTED, FOR ONWARD TRANSMISSION TO THE PURCHASER OR
TRANSFEREE. HOWEVER, SUCH DOCUMENTS SHOULD NOT BE FORWARDED OR TRANSMITTED IN
OR INTO AUSTRALIA, CANADA OR JAPAN.
 
N M Rothschild & Sons Limited, which is regulated by The Securities and
Futures Authority Limited in the UK, is acting for ARCO and ARCO Irish
Holdings in connection with the Offer and no one else and will not be
responsible to anyone other than ARCO and ARCO Irish Holdings for providing
the protections afforded to customers of N M Rothschild & Sons Limited or for
providing advice in relation to the Offer. N M Rothschild & Sons Limited is
acting through Rothschild Inc. for the purposes of making the Offer in the
United States.
 
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                                  Cash Offer
 
                                      by
 
                         N M Rothschild & Sons Limited
 
                                 on behalf of
 
                          ARCO IRISH HOLDINGS [LOGO]
 
                         a wholly owned subsidiary of
 
                                     ARCO
 
                    to acquire the entire share capital of
 
                                Aran Energy plc
 
                  (including all American Depositary Shares)
 
-------------------------------------------------------------------------------
 
The Offer is open for acceptance until 3.00 p.m. (Dublin and London time),
10.00 a.m. (New York City time), on 23 September 1995 (the "initial period")
unless extended (in accordance with the terms thereof). At the conclusion of
the initial period or on or before the conclusion of any extension thereof and
on the satisfaction or, where permitted, waiver of the condition(s) to the
Offer, the purchase of all Aran securities in respect of which the Offer has
been validly accepted and not withdrawn will take place, and the Offer will be
extended for a subsequent period of at least fourteen calendar days. Prior to
the Offer becoming or otherwise being declared unconditional in all respects,
accepting Aran securityholders will have the right to withdraw their
acceptances in respect thereof.
HOWEVER, IN THE EVENT OF THE OFFER BECOMING OR BEING DECLARED UNCONDITIONAL IN
ALL RESPECTS, NO RIGHTS OF WITHDRAWAL WILL BE AVAILABLE TO ACCEPTING ARAN
SECURITYHOLDERS IN THE SUBSEQUENT PERIOD DURING WHICH THE OFFER REMAINS OPEN
FOR ACCEPTANCE.
 
The procedure for acceptance is set out on pages 10 to 13 of this document and
in the accompanying Acceptance Forms.
 
ACCEPTANCES SHOULD BE DESPATCHED AS SOON AS POSSIBLE AND IN ANY EVENT SO AS TO
BE RECEIVED NOT LATER THAN 3.00 P.M. (DUBLIN AND LONDON TIME), 10.00 A.M. (NEW
YORK CITY TIME) ON 23 SEPTEMBER 1995.
 
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     N M ROTHSCHILD & SONS LIMITED                      ROTHSCHILD INC.
           FINANCIAL ADVISER                           US DEALER MANAGER

<PAGE>
 
Rule 8 Notices
 
Any person who, alone or acting together with any other person(s) pursuant to
any agreement or any understanding (whether formal or informal), owns or
controls, or becomes the owner or controller of, directly or indirectly, one
per cent. or more of Aran shares (including Aran shares represented by Aran
ADSs) is generally required under the provisions of Rule 8 of the City Code to
notify the Irish Stock Exchange and the London Stock Exchange of every dealing
in such securities during the initial period of the Offer or until, if later,
the date on which the Offer becomes or is declared unconditional in all
respects, by no later than 12 noon on the business day following the relevant
transaction. Dealings by ARCO, ARCO Irish Holdings or associates (within the
meaning of the City Code) of ARCO or ARCO Irish Holdings in Aran shares or
Aran ADSs must also be so disclosed during the currency of the Offer.
 
Applicable Disclosure Requirements
 
The Offer is made for securities of an Irish company and, while the Offer is
subject to Irish, UK and US disclosure requirements, US investors should be
aware that this document has been prepared in accordance with Irish and UK
format and style, which differs from US format and style. In particular, the
Appendices contain information concerning the Offer responsive to US
disclosure requirements that may be material and has not been summarised
elsewhere. In addition, the summary financial statements of Aran herein have
been prepared in accordance with Irish generally accepted accounting
principles, and thus may not be comparable to financial statements of United
States companies.
 
The information concerning Aran in this document has been extracted from, or
is based upon, publicly available information on file at the Companies
Registration Office in Ireland and the SEC, and other publicly available
information. ARCO and ARCO Irish Holdings have not had access to the books and
records of Aran, were not involved in the preparation of such information and
are not in a position to verify any such information.
 
Enforcement of US Federal Securities Laws
 
ARCO has been advised by its Irish counsel, A&L Goodbody, and by its English
counsel, Clifford Chance, that there is doubt as to the enforceability in
Ireland and England, respectively, in original actions or in actions for
enforcement of judgements of US courts, of liabilities predicated upon the US
federal securities laws.
 
Rule 10b-13 Exemption
 
In accordance with normal UK practice, ARCO Irish Holdings or its nominees or
brokers (acting as agents for ARCO Irish Holdings) or a subsidiary of ARCO
(other than ARCO Irish Holdings) or a special purpose company established and
jointly owned by ARCO and Rothschilds may make certain purchases of Aran
securities outside the United States during the period in which the Offer
remains open for acceptance pursuant to relief granted by the SEC staff from
Rule 10b-13 under the US Exchange Act. Further details on this relief are
contained in Appendix 4 under the heading Market price data and principal
purchases.
 
Offer in United States
 
The Offer is being made in the United States by N M Rothschild & Sons Limited
acting through Rothschild Inc. References in this document to the Offer being
made by N M Rothschild & Sons Limited should be read accordingly.
 
                                       2
<PAGE>
 
Contents
<TABLE>
<CAPTION>
                                                        Page
                                                        ----
<S>                                                     <C>
Letter from the Chairman of ARCO Irish Holdings           5
Letter from Rothschilds
 1.Introduction                                           6
 2.The Offer                                              6
 3.Terms and Conditions of the Offer                      7
 4.Reasons for the Offer                                  7
 5.Financial effects of acceptance of the Offer           7
 6.Information on ARCO                                    8
 7.Information on ARCO Irish Holdings                     8
 8.Information on Aran                                    8
 9.Management and employees                               8
10.Aran share option scheme(s)                            8
11.Taxation                                               9
12.Procedure for acceptance by Aran shareholders         10
13.Procedure for acceptance by holders of Aran ADSs      11
14.Substitute acceptance forms                           14
15.Rights of withdrawal                                  14
16.Settlement                                            14
17.Further information                                   16
Appendices
1.Conditions and Further Terms of the Offer              17
2.Information relating to ARCO and ARCO Irish Holdings   32
3.Information relating to Aran                           41
4.Additional information relevant to the Offer           49
5.Certain provisions of the Irish Companies Act          58
Definitions                                              60
</TABLE>
 
                                       3
<PAGE>
 
                        The Offer is full and generous
 
Capital:
 
-------------------------------------------------------------------------------
<TABLE>
<S>                                                   <C>
For each Aran share                                             IR60p in cash
For each Aran ADS                                     IR(Pounds)18.00 in cash
Premium over Aran share price before the Offer                            41%
Premium over Aran 4 year share price high before the
Offer                                                                     28%
-----------------------------------------------------------------------------
</TABLE>
 
Income:
 
-------------------------------------------------------------------------------
 
Aran shareholders have never received a dividend. Acceptance of the Offer will
provide the opportunity for Aran shareholders to generate income on their
capital for the first time.
-------------------------------------------------------------------------------
 
                   The benefits of the Offer are compelling
 
                        Accept the Offer without delay
 
                                       4
<PAGE>
 
                          ARCO IRISH HOLDINGS [LOGO]
                            515 South Flower Street
                             Los Angeles, CA 90071
 
                                                                 25 August 1995
 
Dear Sir or Madam,
 
On 21 August 1995, the Board of ARCO Irish Holdings announced the terms of a
cash offer for all of Aran's issued and to be issued share capital (including
Aran shares represented by Aran ADSs) at IR60p per share (and IR(Pounds)18.00
per Aran ADS).
 
ARCO is one of the world's leading integrated oil and gas companies, with
corporate headquarters in Los Angeles, California. ARCO and its affiliates
have major operations in the US, the UK, the Netherlands, Indonesia and
Australia. In addition, ARCO has exploration and production operations in 16
other countries including Ireland. ARCO and its affiliates employ
approximately 23,000 people worldwide.
 
ARCO has been active in the UK North Sea and in the waters surrounding Ireland
since 1964 and 1985, respectively. In the UK, ARCO has actively participated
since the first licence round with $1.9 billion invested in exploration and
development activities, and has been involved in exploration activities on 16
Irish blocks with expenditure in Ireland of over $14 million.
 
Historically, ARCO's producing assets were predominantly US based. For a
number of years, ARCO has pursued a strategy of expanding globally its
exploration and production operations. The acquisition of Aran, which would
add complementary assets in the core area of Northwest Europe, is a positive
step in support of this strategy.
 
The Offer represents full and generous value for all of Aran's assets,
including its:
 
 .  core producing assets, the Alba and Gryphon oil fields, where values were
   indicated in recent auction sales of interests in those fields;
 
 .  17.65% interest in block 204/25a, which holds an undetermined unit interest
   in the Schiehallion oil field, where the reserves and the cost of
   development have not yet been defined publicly and must be judged against
   the inherent risks associated with a project at this stage of its
   development in the new and exposed West of Shetlands area; and
 
 .  100% interest in the Connemara oil find, discovered by BP in 1979 but
   subsequently relinquished by BP in 1989, for which considerable appraisal
   work still needs to be done before commerciality can be determined.
 
ARCO has both the financial and technical resources to carry the risk and
exploit these assets successfully.
 
We believe our Offer is full and fair. We strongly urge you to accept it.
 
Yours sincerely,
 
/s/ W. E. Wade
 
Bill Wade
Chairman
 
                                       5
<PAGE>
 
 
                     [N M ROTHSCHILD & SONS LIMITED LOGO]

                         N M ROTHSCHILD & SONS LIMITED

                New Court, St. Swithin's Lane, London EC4P 4DU
 
                                                                 25 August 1995
 
TO ARAN SECURITYHOLDERS AND, FOR INFORMATION ONLY, TO PARTICIPANTS IN THE ARAN
SHARE OPTION SCHEME(S)
 
Dear Sir or Madam,
 
                  CASH OFFER ON BEHALF OF ARCO IRISH HOLDINGS
 
1. INTRODUCTION
 
On 21 August 1995, the Board of ARCO Irish Holdings, a wholly owned subsidiary
of ARCO, announced the terms of a cash offer, to be made by Rothschilds on its
behalf, for the whole of Aran's issued (and to be issued) share capital
(including Aran shares represented by Aran ADSs). This letter sets out the
formal Offer for your Aran securities.
 
The Offer values the existing issued share capital of Aran at approximately
IR(Pounds)157 million (equivalent to Stg(Pounds)160 million).
 
The Offer represents a premium of 41 per cent. over the last dealt price in
Dublin of IR42.5p per Aran share on 18 August 1995, the last business day
prior to the announcement of the Offer.
 
Your attention is drawn to the letter from Bill Wade, the Chairman of the
Board of ARCO Irish Holdings, which appears on page 5 of this document.
 
THE PROCEDURE FOR ACCEPTANCE OF THE OFFER BY HOLDERS OF ARAN SHARES IS SET OUT
IN PARAGRAPH 12 OF THIS LETTER AND BY HOLDERS OF ARAN ADSS IN PARAGRAPH 13 OF
THIS LETTER.
 
2. THE OFFER
 
On behalf of ARCO Irish Holdings, we hereby offer to acquire, on the terms and
subject to the conditions set out in this document and in the Acceptance
Forms, all Aran shares (including the Aran shares represented by Aran ADSs) on
the following bases:
 
             FOR EACH ARAN SHARE                 IR60P IN CASH
                                                 IR(Pounds)18.00 IN CASH
             FOR EACH ARAN ADS 
             (WHICH REPRESENTS 30 ARAN SHARES)
 
Based on an exchange rate of IR(Pounds)1 = Stg(Pounds)1.022, the Offer is
equivalent to Stg61.3p per Aran share and Stg(Pounds)18.40 per Aran ADS. Based
on an exchange rate of IR(Pounds)1=$1.5771, the Offer is equivalent to $0.95
per Aran share and $28.39 per Aran ADS. Paragraph 14 of Appendix 4 sets out
the details of such exchange rates.
 
Whilst the Offer is denominated in Irish pounds, accepting Aran shareholders
and holders of Aran ADSs will instead be entitled to receive their cash
consideration in either pounds sterling or US dollars at prevailing exchange
rates on the latest practicable business day preceding the date of payment.
 
Registered number 925279 England. Registered office as above. Regulated by SFA
 
                                       6
<PAGE>
 
If the Offer becomes or is declared unconditional, it is intended that an
application will be made for the permission granted by the Irish Stock
Exchange and the London Stock Exchange for Aran shares, and by NASDAQ for Aran
ADSs, to be traded on those markets to be revoked. If the Offer becomes or is
declared unconditional and if sufficient acceptances are received, ARCO Irish
Holdings intends to apply the provisions of Section 204 of the Irish Companies
Act to acquire compulsorily any outstanding Aran shares (including Aran shares
represented by Aran ADSs) not acquired pursuant to the Offer or otherwise.
 
3. TERMS AND CONDITIONS OF THE OFFER
 
The Aran shares (including Aran shares represented by Aran ADSs) will be
acquired by ARCO Irish Holdings fully paid and free from all liens, equitable
interests, charges and encumbrances and together with all rights attaching
thereto on or after 21 August 1995, including voting rights and the right to
receive and retain all dividends and other distributions declared, made or
paid on or after 21 August 1995, whether payable in cash or otherwise.
 
The Offer is subject to the relevant conditions and further terms set out in
Appendix 1 of this document and in the Acceptance Forms and to the provisions
relating to acceptance and settlement set out in paragraphs 12, 13 and 16 of
this letter.
 
The Offer will remain open until 3.00 p.m. (Dublin and London time), 10.00
a.m. (New York City time) on 23 September 1995, or such later time(s) and/or
date(s) as ARCO Irish Holdings may decide.
 
THE OFFER IS CONDITIONAL, INTER ALIA, ON VALID ACCEPTANCES BEING RECEIVED IN
RESPECT OF NOT LESS THAN 95 PER CENT. OF THE ARAN SHARES (INCLUDING ARAN
SHARES REPRESENTED BY ARAN ADSs) TO WHICH THE OFFER RELATES, OR SUCH LESSER
PERCENTAGE AS ARCO IRISH HOLDINGS MAY DECIDE (THE "ACCEPTANCE LEVEL"),
PROVIDED THAT SUCH CONDITION (THE "ACCEPTANCE CONDITION") SHALL NOT BE
SATISFIED UNLESS THE MINIMUM ACCEPTANCE CONDITION SHALL HAVE BEEN SATISFIED.
ANY INTENTION TO REDUCE THE ACCEPTANCE LEVEL WILL BE ANNOUNCED BY ARCO IRISH
HOLDINGS AT LEAST THREE US BUSINESS DAYS PRIOR TO THE DATE ON WHICH SUCH
REDUCTION BECOMES EFFECTIVE. ARCO IRISH HOLDINGS WILL NOT, HOWEVER,
NECESSARILY CAUSE THE OFFER TO REMAIN OPEN FOR ANY MINIMUM PERIOD AFTER SUCH
REDUCTION OF THE ACCEPTANCE LEVEL HAS BECOME EFFECTIVE UNLESS THE OFFER
BECOMES OR IS DECLARED UNCONDITIONAL IN ALL RESPECTS IN WHICH EVENT IT WILL
REMAIN OPEN FOR ACCEPTANCE FOR A FURTHER PERIOD OF NOT LESS THAN 14 DAYS.
 
4. REASONS FOR THE OFFER
 
The background to and reasons for the Offer are set out in the letter from
Bill Wade, the Chairman of the Board of ARCO Irish Holdings, on page 5 and in
Appendix 4 of this document.
 
5. FINANCIAL EFFECTS OF ACCEPTANCE OF THE OFFER
 
(a) Capital
 
The following table shows, for illustrative purposes only and on the bases and
assumptions set out in the notes below, the financial effects of acceptance of
the Offer on the capital value for a holder of 100 Aran shares, if the Offer
becomes or is declared unconditional in all respects.
 
<TABLE>
<CAPTION>
                                 Notes    IR(Pounds)    Stg(Pounds)(ii)
<S>                              <C>      <C>           <C>
Cash consideration                          60.00           61.32
Market value of 100 Aran shares  (iii)      42.50           43.44
                                            -----           -----
Increase in capital value                   17.50           17.88
                                            -----           -----
THIS REPRESENTS AN INCREASE OF                41%             41%
</TABLE>
-------
Notes:
(i)   No account has been taken of any potential liability to taxation.
(ii)  The Stg(Pounds) equivalent is based on the exchange rate set out in
      paragraph 14 of Appendix 4.
(iii) The market value shown in the table for Aran shares is based on the last
      dealt price in Dublin of IR42.5p per Aran share on 18 August 1995, being
      the last dealing day before the announcement of the Offer, as derived
      from the Irish Stock Exchange Official List.
 
 
                                       7
<PAGE>
 
(b) Income
 
Aran shareholders have never received a dividend. Acceptance of the Offer will
provide the opportunity for Aran shareholders to generate income from their
capital for the first time.
 
6. INFORMATION ON ARCO
 
ARCO is a worldwide, integrated hydrocarbons corporation with operations and
subsidiaries encompassing all aspects of the oil and gas business including
exploration, production and marketing of crude oil, natural gas and natural
gas liquids, and refining, marketing and transportation of petroleum products.
ARCO also mines and markets coal and has interests in two petrochemical
companies. It is based in California and has major operations in Alaska,
California, Washington and the Gulf Coast as well as in the UK, the
Netherlands, Indonesia and Australia and employs approximately 23,000 people
worldwide. ARCO's common stock is listed on the New York, Zurich and London
Stock Exchanges.
 
For the year ended 31 December 1994, ARCO reported consolidated net income
after tax of $919 million on consolidated total revenue of $17.2 billion.
Consolidated stockholders' equity as at 31 December 1994 amounted to $6.3
billion. In the six months to 30 June 1995, ARCO reported unaudited
consolidated net income after tax of $713 million on unaudited consolidated
total revenue of $9.1 billion. Unaudited consolidated stockholders' equity as
at 30 June 1995 amounted to $6.6 billion.
 
Further information on ARCO is set out in Appendix 2.
 
7. INFORMATION ON ARCO IRISH HOLDINGS
 
ARCO Irish Holdings is a wholly owned subsidiary of ARCO, incorporated in
Delaware, US on 2 August 1995 for the purpose of making the Offer. To date,
ARCO Irish Holdings has engaged in no activities other than those incidental
to its organisation and the making of the Offer.
 
Certain information on the directors and executive officers of ARCO Irish
Holdings is set out in Appendix 2.
 
8. INFORMATION ON ARAN
 
Aran explores for, develops and produces oil and gas. The Aran Group's
principal activities are in the UK offshore sector (including the North Sea),
the US Gulf Coast area and offshore Ireland. Aran's registered office is in
Dublin, Ireland, and Aran has its principal operating units in London and
Houston. Aran shares are listed on the Irish Stock Exchange and the London
Stock Exchange and Aran ADSs are quoted on NASDAQ.
 
For the year ended 31 December 1994, Aran reported consolidated after tax
profit of IR(Pounds)3.7 million on turnover of IR(Pounds)83.4 million and had
consolidated shareholders' funds at that date of IR(Pounds)80.0 million. It
employed an average of 39 people during 1994.
 
Further information on Aran is set out in Appendix 3.
 
9. MANAGEMENT AND EMPLOYEES
 
The existing employment rights, including pension rights, of the management
and employees of the Aran Group will be fully safeguarded.
 
10. ARAN SHARE OPTION SCHEME(S)
 
The Offer will extend to any Aran securities unconditionally allotted or
issued and fully paid prior to the date on which the Offer becomes or is
declared unconditional (or such later date or dates as ARCO Irish Holdings may
decide) pursuant to the exercise of options granted under the Aran share
option scheme(s). Appropriate proposals will be made by ARCO Irish Holdings in
due course to holders of options under the Aran share option scheme(s).
 
 
                                       8
<PAGE>
 
11. TAXATION
 
ANY HOLDERS OF ARAN SECURITIES WHO ARE IN ANY DOUBT AS TO THEIR TAX POSITION
SHOULD CONSULT THEIR PROFESSIONAL ADVISER.
 
The following paragraphs are intended as a general guide only and are based on
current legislation and tax authority practice (which may change) and may not
apply to certain categories of Aran securityholders (e.g. dealers in
securities).
 
(a) Irish taxation
 
For holders of Aran securities who are resident or ordinarily resident in
Ireland for tax purposes or who carry on business in Ireland through a branch
or agency to which such Aran securities are attributable, the sale of such
Aran securities pursuant to the Offer will constitute a disposal for the
purposes of Irish taxation of capital gains. Such a disposal may, depending on
the individual circumstances of such holders, give rise to a liability to
taxation.
 
A person who is neither resident nor ordinarily resident in Ireland is not
normally subject to Irish capital gains tax on the disposal of Irish assets.
If at the time of any disposal of Aran shares, such shares were not quoted on
a stock exchange and derived their value or the greater part of their value
directly or indirectly from Irish land, buildings or mineral rights, then such
disposal could be subject to Irish capital gains tax notwithstanding that the
person making the disposal is neither resident nor ordinarily resident in
Ireland.
 
(b) UK taxation of capital gains
 
For holders of Aran securities who are resident or ordinarily resident in the
UK for tax purposes or who carry on business in the UK through a branch or
agency to which such Aran securities are attributable and who hold their
shares as an investment, the sale of such Aran securities pursuant to the
Offer will constitute a disposal for the purposes of UK taxation of capital
gains. Such a disposal may, depending on the individual circumstances of such
holders, give rise to a liability to taxation.
 
(c) US taxation
 
The summary below addresses certain US federal income tax consequences
applicable to holders of Aran securities who are citizens or residents of the
United States, domestic corporations or otherwise taxed as United States
residents.
 
The receipt of cash pursuant to the Offer will be a taxable transaction for US
federal income tax purposes and may also be a taxable transaction under
applicable state, local, foreign and other tax laws.
 
In general, a holder of Aran securities who sells such securities pursuant to
the Offer will, for US federal income tax purposes, recognise a gain or loss
equal to the difference between such holder's adjusted tax basis in the Aran
securities transferred and the amount of cash received in exchange therefor.
Such gain or loss will generally be capital gain or loss and will be long-term
capital gain or loss if, on the date of sale, the Aran securities were held
for more than one year. A holder of Aran securities who sells such securities
pursuant to the Offer may have a foreign currency exchange gain or loss for US
federal income tax purposes which would be treated as ordinary income or loss.
Any such exchange gain or loss would be in addition to the gain or loss
recognised by the holder on the disposition of Aran securities pursuant to the
Offer.
 
Further information on the application of US taxation is contained in
paragraph 12 of Appendix 4.
 
 
                                       9
<PAGE>
 
(d) Other jurisdictions
 
Aran securityholders who are subject to taxation in jurisdictions other than
Ireland, the UK or the US should consult their professional adviser before
taking action.
 
12. PROCEDURE FOR ACCEPTANCE BY ARAN SHAREHOLDERS
 
TO ACCEPT THE OFFER IN RESPECT OF ARAN SHARES you must complete Boxes 1 and 3,
and if appropriate Boxes 4 and/or 5, 6 or 7 and sign Box 2 of the Form of
Acceptance IN THE PRESENCE OF A WITNESS, who should also sign in accordance
with the instructions printed thereon. Further details for accepting the Offer
are set out below. Details for accepting the Offer in respect of Aran ADSs are
set out in paragraph 13 of this letter.
 
Aran securityholders who hold both Aran shares and Aran ADSs should use the
appropriate Acceptance Form in respect of each holding.
 
(a) Return of the Form of Acceptance
 
The completed, signed and witnessed Form of Acceptance, together with your
share certificate(s) and/or other document(s) of title, should be returned by
hand or by post to the Irish Receiving Agent, AIB Bank, Registrars' & New
Issue Department, Bankcentre, P.O. Box 954, Ballsbridge, Dublin 4, or the UK
Receiving Agent, The Royal Bank of Scotland plc, Registrar's Department, New
Issues Section, PO Box 859, Consort House, East Street, Bedminster, Bristol,
BS99 1XZ or, by hand only (during normal business hours only), to The Royal
Bank of Scotland plc, Registrar's Department, New Issues Section, 67 Lombard
Street, London EC3P 3DL. IN THE ABSENCE OF ELECTIONS BEING MADE TO RECEIVE
ALTERNATIVE CURRENCIES, THE CURRENCY IN WHICH YOU RECEIVE YOUR CONSIDERATION
WILL DEPEND ON YOUR REGISTERED ADDRESS. DETAILS OF CURRENCY ARRANGEMENTS ARE
SET OUT IN PARAGRAPH 16 OF THIS LETTER.
 
An Aran shareholder may, if more convenient, instead submit the Form of
Acceptance, together with his or her share certificate(s) and/or other
document(s) of title, to the US Depositary, First Chicago Trust Company of New
York, either by hand or overnight courier to Suite 4680, 14 Wall Street,
Eighth Floor, New York, NY 10005 or by post to Suite 4660, P.O. Box 2559,
Jersey City, NJ 07303 who will receive such Form(s) of Acceptance and
certificates and/or other documents of title on behalf of the UK Receiving
Agent and the Irish Receiving Agent.
 
Completed documents should be received by either the Irish Receiving Agent,
the UK Receiving Agent or the US Depositary as soon as possible and in any
event so as to be received NOT LATER THAN 3.00 P.M. (DUBLIN AND LONDON TIME),
10.00 A.M. (NEW YORK CITY TIME) ON 23 SEPTEMBER 1995. Aran shareholders with
an Irish or a UK registered address will find enclosed a reply-paid envelope
for this purpose. No acknowledgement of receipt of documents will be given.
The instructions printed on the Forms of Acceptance shall be deemed to form
part of the terms of the Offer.
 
(b) Share certificates not readily available or lost
 
Even if your share certificate(s) and/or other document(s) of title is/are not
readily available or is/are lost, the Form of Acceptance should nevertheless
be completed, signed and returned as stated above so as to be received NOT
LATER THAN 3.00 P.M. (DUBLIN AND LONDON TIME), 10.00 A.M. (NEW YORK CITY TIME)
ON 23 SEPTEMBER 1995 and the share certificate(s) and/or other document(s) of
title forwarded as soon as possible thereafter.
 
 
                                      10
<PAGE>
 
The completed Form of Acceptance, together with any share certificate(s)
and/or other document(s) of title that you may have available, should be
lodged with the Irish Receiving Agent or the UK Receiving Agent or (if
appropriate) the US Depositary, at the relevant address given above,
accompanied by a letter stating that the balance will follow or that you have
lost one or more of your share certificate(s) and/or other document(s) of
title.
 
In the case of loss, you should then write to Aran's registrars, Bank of
Ireland, Registration Department, P.O. Box 4044, Hume House, Ballsbridge,
Dublin 4, Ireland, advising them of the loss and asking for a letter of
indemnity for the lost share certificate(s) which, when completed in
accordance with the instructions given, should be returned to the Irish
Receiving Agent or the UK Receiving Agent or (if appropriate) the US
Depositary at the relevant address given above.
 
(c) Validity of acceptances
 
Even if your Form of Acceptance is received not complete in all respects or is
not accompanied by the relevant share certificates and/or other document(s) of
title or your acceptance of the Offer is in some other way defective ARCO
Irish Holdings and Rothschilds reserve the right (subject to the terms of the
Offer) to treat any acceptance of the Offer as valid. In that event, the
consideration under the Offer will not be despatched until after the Form of
Acceptance is complete in all respects and the share certificate(s) and/or
other document(s) of title or indemnities satisfactory to ARCO Irish Holdings
and Rothschilds has/have been received.
 
(d) Overseas Aran shareholders
 
The attention of Aran shareholders not resident in Ireland, the UK or the US
(and any person, including without limitation, any custodian, nominee or
trustee who may have an obligation to forward this document or any Acceptance
Forms outside Ireland, the UK or the US) is drawn to paragraph 9 (Overseas
holders of Aran shares and Aran ADSs) of Part B of Appendix 1. In particular,
such documents should not be forwarded or transmitted in or into Australia,
Canada or Japan.
 
(e) Method of delivery
 
The method of delivery of Aran shares and all other required documents is at
the option and risk of the accepting Aran shareholder. If delivery is by mail,
registered mail with return receipt requested, properly insured, is
recommended. In all cases, sufficient time should be allowed to ensure timely
delivery. No acknowledgement of receipt of documents will be given.
 
Further information regarding procedures for acceptance by Aran shareholders
is set out in paragraph 3 of Part B of Appendix 1.
 
If you are in any doubt about the procedure for acceptance please telephone
the Irish Receiving Agent on 01 660 0311 (Ext. 12280), or the UK Receiving
Agent on 0117 937 0666, or the US Depositary on (800) 659 6111 (toll free) or
(201) 324 0137.
 
13. PROCEDURE FOR ACCEPTANCE BY HOLDERS OF ARAN ADSS
 
(a) To accept the Offer for Aran ADSs
 
For a holder of Aran ADSs validly to accept the Offer:
 
   (i) either a properly completed and duly executed Letter of Transmittal
       (or facsimile thereof), together with any required signature
       guarantees and any other required documents, must be received by the
       US Depositary at one of its addresses set out on the back cover of
       this document, and the Aran ADRs evidencing such Aran ADSs must be
       received by the US Depositary at one of such addresses or delivered
       pursuant to the procedures for book-entry transfer set out in
       paragraph 4 of Part B of Appendix 1 (and a confirmation of receipt of
       such transfer received by the US Depositary); or
 
                                      11
<PAGE>
 
   (ii) such holder must comply with the guaranteed delivery procedures set
        out in paragraph 4 of Part B of Appendix 1.
 
   Delivery of a Letter of Transmittal, the Aran ADRs evidencing tendered
   Aran ADSs (or book-entry transfer of such Aran ADSs) and any other
   required documents to the US Depositary by a holder of Aran ADSs holder
   will be deemed (without any further action by the US Depositary) to
   constitute an acceptance of the Offer by such holder in respect of such
   holder's Aran ADSs, subject to the terms and conditions set out in this
   document and in the Letter of Transmittal. The acceptance of the Offer by
   a holder of Aran ADSs pursuant to the procedures described above, subject
   to the withdrawal rights described below, will constitute a binding
   agreement between such holder of Aran ADSs and ARCO Irish Holdings upon
   the terms and subject to the conditions of the Offer. If acceptance has
   been made in respect of an Aran ADS then a separate acceptance in respect
   of the Aran shares represented by such Aran ADS may not be made.
 
   COMPLETED LETTERS OF TRANSMITTAL, ARAN ADRS EVIDENCING TENDERED ARAN ADSs
   (OR CONFIRMATION OF A BOOK-ENTRY TRANSFER OF SUCH ARAN ADSs) AND ANY
   OTHER REQUIRED DOCUMENTS SHOULD BE RECEIVED BY THE US DEPOSITARY AS SOON
   AS POSSIBLE AND IN ANY EVENT BY NOT LATER THAN 10.00 A.M. (NEW YORK CITY
   TIME), 3.00 P.M. (DUBLIN AND LONDON TIME) ON 23 SEPTEMBER 1995. NO
   ACKNOWLEDGEMENT OF RECEIPT OF DOCUMENTS WILL BE GIVEN. THE INSTRUCTIONS
   PRINTED ON THE LETTER OF TRANSMITTAL SHALL BE DEEMED TO FORM PART OF THE
   TERMS OF THE OFFER.
 
(b) Partial acceptances
 
If the Offer is to be accepted in respect of less than all of the Aran ADSs
evidenced by any Aran ADRs delivered to the US Depositary, then the holder
thereof should so indicate in the Letter of Transmittal by filling in the
number of Aran ADSs in respect of which the Offer is being accepted in the Box
entitled "Description of Accepting Aran ADSs." In such case, in the event of
the Offer becoming unconditional, a new Aran ADR for the remainder of the Aran
ADSs (in respect of which the Offer was not accepted) represented by the old
Aran ADR will be sent to the person(s) signing such Letter of Transmittal (or
delivered as such person properly indicates thereon) as promptly as
practicable following the date on which the Aran ADSs in respect of which the
Offer had been accepted are purchased.
 
(c) Guaranteed delivery
 
If a holder of Aran ADSs wishes to accept the Offer and the Aran ADRs
evidencing such ADSs are not immediately available or the procedures for book-
entry transfer cannot be completed on a timely basis, or if time will not
permit all required documents to reach the US Depositary prior to the expiry
of the Offer, such holder's acceptance of the Offer may nevertheless be
effected using the guaranteed delivery procedures set out in paragraph 4 of
Part B of Appendix 1. Holders of Aran ADSs who deliver a Notice of Guaranteed
Delivery to accept the Offer must, inter alia, effect the deliveries described
in paragraph 13(a)(i) of this letter within three trading days after the date
of execution of such Notice of Guaranteed Delivery. For these purposes, a
"trading day" is any day on which NASDAQ is open for business.
 
COMPLETED NOTICES OF GUARANTEED DELIVERY SHOULD BE RECEIVED BY THE US
DEPOSITARY AS SOON AS POSSIBLE AND IN ANY EVENT BY NOT LATER THAN 10.00 A.M.
(NEW YORK CITY TIME), 3.00 P.M. (DUBLIN AND LONDON TIME) ON 23 SEPTEMBER 1995.
NO ACKNOWLEDGEMENT OF RECEIPT OF DOCUMENTS WILL BE GIVEN. THE INSTRUCTIONS
PRINTED ON THE NOTICE OF GUARANTEED DELIVERY SHALL BE DEEMED TO FORM PART OF
THE TERMS OF THE OFFER.
 
                                      12
<PAGE>
 
HOWEVER, RECEIPT OF A NOTICE OF GUARANTEED DELIVERY WILL NOT BE TREATED AS A
VALID ACCEPTANCE FOR THE PURPOSE OF SATISFYING THE ACCEPTANCE CONDITION. FOR
SUCH ARAN SECURITYHOLDER'S ACCEPTANCE TO BE COUNTED TOWARDS SATISFACTION OF
THE ACCEPTANCE CONDITION, THE US DEPOSITARY MUST HAVE BEEN RECEIVED, BY NOT
LATER THAN 10.00 A.M. (NEW YORK CITY TIME), 3.00 P.M. (DUBLIN AND LONDON TIME)
ON 23 SEPTEMBER 1995:
 
   (i) the Aran ADRs evidencing the Aran ADSs referred to in the Notice of
       Guaranteed Delivery; or
 
   (ii) in the case of Aran ADSs held in book-entry form, timely
        confirmation of a book-entry transfer of such Aran ADSs into the US
        Depositary's account at a Book-Entry Transfer Facility pursuant to
        the procedures set out in paragraph 4 of Part B of Appendix 1,
 
and, in either case, together with a properly completed and duly executed
Letter of Transmittal (or facsimile thereof) with any required signature
guarantees and any other required documents.
 
Holders of Aran ADSs who deliver a Notice of Guaranteed Delivery to accept the
Offer must deliver a Letter of Transmittal at a later date when delivering
Aran ADSs to the US Depositary, as provided herein. Aran securityholders who
hold both Aran shares and Aran ADSs should use the appropriate Acceptance Form
in respect of each holding.
 
(d) Validity of acceptances
 
Even if your Letter of Transmittal or Notice of Guaranteed Delivery, together
with any signature guarantees, are received not complete in all respects or
(unless book-entry transfer of Aran ADSs has been made) your Letter of
Transmittal is not accompanied by the Aran ADRs evidencing tendered Aran ADSs
and/or other documents(s) of title, or your acceptance of the Offer is in some
other way defective, ARCO Irish Holdings and Rothschilds reserve the right
(subject to the terms of the Offer) to treat any acceptance of the Offer as
valid. In that event, the consideration under the Offer will not be despatched
until after the Letter of Transmittal, together with any required signature
guarantees, are complete in all respects, and such Aran ADRs and/or other
document(s) of title or indemnities satisfactory to ARCO Irish Holdings and
Rothschilds has/have been received.
 
(e) Overseas Aran ADS holders
 
The attention of holders of Aran ADSs not resident in Ireland, the UK or the
US (and any person, including without limitation, any custodian, nominee or
trustee who may have an obligation to forward this document or any Acceptance
Forms outside Ireland, the UK or the US) is drawn to paragraph 9 (Overseas
holders of Aran shares and Aran ADSs) of Part B of Appendix 1. In particular,
such documents should not be forwarded or transmitted in or into Australia,
Canada or Japan.
 
(f) Method of delivery
 
The method of delivery of Aran ADSs and all other required documents is at the
option and risk of the accepting Aran ADS holder. If delivery is by mail,
registered mail with return receipt requested, properly insured, is
recommended. In all cases, sufficient time should be allowed to ensure timely
delivery. No acknowledgement of receipt of documents will be given.
 
Further information regarding procedures for acceptance by holders of Aran
ADSs is set out in paragraph 4 of Part B of Appendix 1.
 
If you are in any doubt about the procedure for acceptance by holders of Aran
ADSs please telephone the US Depositary on (800) 659 6111 (toll free) or (201)
324 0137.
 
 
                                      13
<PAGE>
 
14. SUBSTITUTE ACCEPTANCE FORMS
 
Aran shareholders are being sent a Form of Acceptance which they must use to
accept the Offer in respect of their Aran shares in accordance with the terms
of paragraph 12 above.
 
Holders of Aran ADSs are being sent a Letter of Transmittal and a Notice of
Guaranteed Delivery, which they must use to accept the Offer in respect of
their Aran ADSs in accordance with the terms of paragraph 13 above.
 
Should any Aran securityholder receive an incorrect Acceptance Form with which
to accept the Offer, or need any additional Acceptance Forms, he or she should
contact the Irish Receiving Agent, the UK Receiving Agent or the US Depositary
(at the relevant address and telephone number set out on the back cover of
this document), who will provide the appropriate Acceptance Forms.
 
15. RIGHTS OF WITHDRAWAL
 
With certain exceptions pursuant to an SEC exemptive order, the Offer is
subject to the US tender offer rules applicable to securities registered under
the US Exchange Act as well as to the rules of the City Code. This has
necessitated a number of changes from the procedures which normally apply to
offers for Irish companies, including those applicable to offeree
shareholders' rights to withdraw their acceptance of an offer.
 
Under the Offer, holders of Aran securities will be able to withdraw their
acceptances at any time prior to the Offer becoming or being declared
unconditional in all respects, which in any event will not be prior to 3.00
p.m. (Dublin and London time), 10.00 a.m. (New York City time) on 23 September
1995. Withdrawals of acceptances in respect of the Offer may not be rescinded
without the consent of ARCO Irish Holdings or Rothschilds and the Offer will
be deemed not to have been validly accepted in respect of any Aran securities
which have been so withdrawn. However, the Offer may be accepted again in
respect of the withdrawn Aran securities by following one of the procedures
described above in paragraph 12 (Procedure for acceptance by Aran
shareholders) or paragraph 13 (Procedure for acceptance by holders of Aran
ADSs), as appropriate, at any time prior to the expiry or lapse of the Offer.
 
All questions as to the validity (including time of receipt) of notices of
withdrawal will be determined by ARCO Irish Holdings, whose determination
(except as required by the Panel) will be final and binding. None of ARCO
Irish Holdings, Rothschilds, the Irish Receiving Agent, the UK Receiving
Agent, the US Depositary, the US Dealer Manager, or any other person will be
under any duty to give notification of any defects or irregularities in any
notice of withdrawal or incur any liability for failure to give any such
notification.
 
Further details of these rights of withdrawal and the procedure for effecting
withdrawals are set out in paragraph 6 (Rights of withdrawal) of Part B of
Appendix 1.
 
16. SETTLEMENT
 
(a) Date of payment
 
The settlement procedure with respect to the Offer will be consistent with
Irish and UK practice, which differs from the US tender offer rules in certain
material respects, particularly with regard to the date of payment.
 
Subject to the Offer becoming or being declared unconditional in all respects,
cheques drawn on a branch of The Royal Bank of Scotland plc will be sent by
first class post to accepting Aran
 
                                      14
<PAGE>
 
shareholders, and cheques drawn on First Chicago Trust Company of New York
will be sent by post to accepting holders of Aran ADSs or other designated
agents, in each case at the risk of the persons entitled thereto:
 
   (i)  in the case of acceptances received complete in all respects by the
        date when the Offer becomes or is declared unconditional in all
        respects, within 21 days of such date; or
 
   (ii) in the case of acceptances received complete in all respects after
        such date but while the Offer remains open for acceptance, within 21
        days of such receipt.
 
(b) Currency of consideration
 
Whilst the Offer price per Aran share is denominated in Irish pounds, Aran
shareholders with registered addresses in the UK will (subject to paragraph
16(c) below) receive the cash consideration due to them in pounds sterling.
 
Whilst the Offer price per Aran ADS is denominated in Irish pounds, holders of
Aran ADSs will (subject to paragraph 16(c) below) receive the cash
consideration due to them in US dollars.
 
All other accepting Aran shareholders will (subject to paragraph 16(c) below)
receive the cash consideration due to them in Irish pounds.
 
(c) Alternative currency election
 
Accepting Aran securityholders may elect, instead of receiving the currency
set out in paragraph 16(b) above, to receive all (but not part) of the cash
consideration due to them in one of the other two currencies referred to in
paragraph 16(b) above:
 
   (i)Irish pounds payment election
   Accepting Aran shareholders with registered addresses in the UK and
   accepting holders of Aran ADSs who wish to receive their cash
   consideration in Irish pounds should put a "X" in the Box of the relevant
   Acceptance Form entitled Irish Pounds Payment Election.
 
   (ii)Pounds sterling payment election
   Accepting Aran shareholders with registered addresses outside the UK and
   accepting holders of Aran ADSs who wish to receive their cash
   consideration in pounds sterling should put a "X" in the Box of the
   relevant Acceptance Form entitled Pounds Sterling Payment Election.
 
   The amount of pounds sterling received will be at the noon buying rate
   prevailing in London for transfers in Irish pounds on the latest
   practicable business day preceding the date of despatch of payment as
   certified by The Royal Bank of Scotland plc. All costs of conversion will
   be paid by ARCO Irish Holdings.
 
   The actual amount of pounds sterling received will depend upon the
   exchange rate prevailing on the latest practicable business day preceding
   the date of despatch of payment, which may differ from the exchange rate
   set forth in paragraph 2 above. Aran securityholders should also be aware
   that the exchange rate which is prevailing at the date on which an
   election is made to receive pounds sterling and/or on the date of
   despatch of payment may be different from that prevailing on the latest
   practicable business day preceding the date of despatch of payment. IN
   ALL CASES, FLUCTUATIONS IN THE IRISH POUNDS/POUNDS STERLING EXCHANGE RATE
   ARE AT THE RISK OF ACCEPTING ARAN SECURITYHOLDERS WHO WILL, OR WHO ELECT
   TO, RECEIVE THEIR CONSIDERATION IN POUNDS STERLING.
 
   (iii)US dollars election
   Accepting Aran shareholders who wish to receive their cash consideration
   in US dollars should put a "X" in the Box of their Form of Acceptance
   entitled US Dollars Payment Election.
 
                                      15
<PAGE>
 
   The amount of US dollars received will be at the noon buying rate
   prevailing in London for transfers in Irish pounds on the latest
   practicable business day preceding the date of despatch of payment as
   certified by The Royal Bank of Scotland plc. All costs of conversion will
   be paid by ARCO Irish Holdings.
 
   The actual amount of US dollars received will depend upon the exchange
   rate prevailing on the latest practicable business day preceding the date
   of despatch of payment, which may differ from the exchange rate set forth
   in paragraph 2 above. Aran securityholders should also be aware that the
   exchange rate which is prevailing at the date on which an election is
   made to receive US dollars and/or on the date of despatch of payment may
   be different from that prevailing on the latest practicable business day
   immediately preceding the date of despatch of payment. IN ALL CASES,
   FLUCTUATIONS IN THE IRISH POUNDS/US DOLLAR EXCHANGE RATE ARE AT THE RISK
   OF ACCEPTING ARAN SHAREHOLDERS WHO WILL, OR WHO ELECT TO, RECEIVE THEIR
   CONSIDERATION IN US DOLLARS.
 
(d) General
 
All documents and remittances sent by or to Aran securityholders will be sent
at their own risk. If the Offer does not become or is not declared
unconditional in all respects, share certificate(s), Aran ADRs and/or other
document(s) of title, together with the Acceptance Forms, will be returned by
post (or such other method as may be approved by the Panel) within 14 days of
the Offer lapsing to the person or agent whose name and address is set out in
the relevant Box of the Acceptance Form (which must be outside Australia,
Canada and Japan) or, if none is set out, to the first-named holder at his/her
registered address outside Australia, Canada and Japan, or in the case of Aran
ADSs delivered pursuant to the book-entry transfer procedures, as described in
Appendix 1.
 
No such documents nor any remittances under the Offer will be sent to an
address in Australia, Canada or Japan.
 
17. FURTHER INFORMATION
 
Your attention is drawn to the further information in the Appendices which
form part of this document.
 
                               Yours very truly,
                             for and on behalf of
                         N M Rothschild & Sons Limited
 
                               Nicholas Wrigley
                                   Director
 
                                      16
<PAGE>
 
APPENDIX 1
 
Conditions and Further Terms of the Offer
 
The Offer is being made in accordance with and subject to the provisions of
the City Code and the applicable rules and regulations of the SEC.
 
The following conditions and further terms apply to the Offer.
 
Except where the context otherwise requires, references in this Appendix 1 and
in the Acceptance Forms:
 
   (a) to "the Offer" shall include any extension or revision or amendment
       of the Offer and shall also include any alternative or election
       available in connection with Offer;
 
   (b) to "the Offer becoming unconditional" shall be construed as
       references to the Offer becoming or being declared unconditional in
       all respects and references to becomes unconditional shall be
       construed accordingly; and
 
   (c) to "acceptances" of the Offer shall include deemed acceptances of the
       Offer.
 
PART A--CONDITIONS OF THE OFFER
 
The Offer is subject to the following conditions:
 
   (a) valid acceptances being received (and not withdrawn) by 3.00 p.m.
       (Dublin and London time), 10.00 a.m. (New York City time) on 23
       September 1995 (or such later time(s) and/or date(s) as ARCO Irish
       Holdings may, subject to the rules of the City Code, decide) in
       respect of not less than 95 per cent. (or such lesser percentage as
       ARCO Irish Holdings may decide) of the Aran shares to which the Offer
       relates provided that this condition shall not be satisfied unless
       ARCO Irish Holdings and/or its wholly owned subsidiaries shall have
       acquired or agreed to acquire, pursuant to the Offer or otherwise,
       Aran shares (including Aran shares represented by Aran ADSs) carrying
       more than 50 per cent. of the voting rights normally exercisable at
       general meetings of Aran, including, for this purpose, any such
       voting rights attaching (or which on issue will attach) to any Aran
       shares (including Aran shares represented by Aran ADSs)
       unconditionally allotted or issued before this condition is satisfied
       whether pursuant to the exercise of any outstanding subscription or
       conversion rights or otherwise; and for this purpose the expression
       "Aran shares to which the Offer relates" means the aggregate of Aran
       shares (including Aran shares represented by Aran ADSs) which have
       been unconditionally allotted or issued before the date on which the
       Offer is made and Aran shares allotted after that date but on or
       before the date upon which the Offer becomes or is declared
       unconditional (or such later date as ARCO Irish Holdings may decide)
       but excluding Aran shares which at the date of the Offer were in the
       beneficial ownership or deemed to be in the beneficial ownership
       (under Section 204 of the Irish Companies Act) of ARCO Irish
       Holdings;
 
   (b) the Minister for Enterprise and Employment of Ireland having stated
       in writing that he does not intend to make an order under Section 9
       of the Mergers, Take-overs and Monopolies (Control) Act, 1978 (as
       amended) of Ireland (the "Mergers Act") in relation to the Offer or,
       in the event of the said Minister making an order subject to
       conditions, ARCO Irish Holdings in its absolute discretion having
       decided to accept such conditions or, in the event of no such order
       being made and the said Minister not stating in writing that he does
       not intend to make such an order, the relevant period within the
       meaning of Section 6 of the Mergers Act having expired;
 
   (c) the Minister for Transport, Energy and Communications of Ireland
       granting such assurances, confirmations, consents, approvals or
       authorisations as may be required to ensure that none of the
       petroleum prospecting licences, licensing options, exploration
       licences, lease undertakings, petroleum leases and/or reserved area
       licences held by Aran and/or any other member of the Wider Aran Group
       will be revoked, altered or terminated as a result of the Offer or
       the acquisition of Aran securities by ARCO Irish Holdings pursuant to
       the Offer;
 
   (d) it being established in terms satisfactory to ARCO Irish Holdings
       that the proposed acquisition of Aran by ARCO Irish Holdings or any
       matters arising therefrom will not be referred to the UK Monopolies
       and Mergers Commission;
 
                                      17
<PAGE>
 
   (e) the SEC having given and not having rescinded or revoked, in whole or
       in part, any necessary or desirable exemptive relief under the US
       Exchange Act with respect to the Offer;
 
   (f) the UK Department of Trade and Industry having given such assurances
       as may be required to ensure that none of the exploration or
       production licences held by Aran and/or any other members of the
       Wider Aran Group will be revoked, and that no further change in
       control of the licensee will be required, in each case as a result of
       the Offer or the proposed acquisition by ARCO Irish Holdings of any
       Aran shares (including Aran shares represented by Aran ADSs);
 
   (g) ARCO Irish Holdings not having discovered that, except as disclosed
       in the accounts of Aran for the year ended 31 December 1994 or in any
       information which has been publicly announced by Aran prior to
       17 August 1995:
 
     (i)   any past or present member of the Wider Aran Group has not
           complied with all applicable legislation or regulations of any
           jurisdiction with regard to the disposal, discharge, spillage,
           leak or emission of any waste or hazardous substance or any
           substance likely to impair the environment or harm human health
           which non-compliance would be likely to give rise to a liability
           (whether actual or contingent) on the part of any member of the
           Wider Aran Group;
 
     (ii)  (1) there has been a disposal, spillage or leak of waste or
           hazardous substance or any substance likely to impair the
           environment or harm human health on; or
 
           (2) there has been an emission or discharge of any waste or
           hazardous substance or any substance likely to impair the
           environment or harm human health from,
 
           any land or other asset now or previously owned, occupied or made
           use of by any past or present member of the Wider Aran Group which
           would be likely to give rise to a liability (whether actual or
           contingent) on the part of any member of the Wider Aran Group;
 
     (iii) there is any liability (whether actual or contingent) to make
           good, repair, re-instate or clean up any property now or
           previously owned, occupied or made use of by any past or present
           member of the Wider Aran Group under any environmental
           legislation, regulation, notice, circular or order of any
           government, quasi-government, state or local government,
           supranational, statutory or regulatory body, court, agency or
           association or any other public body in any jurisdiction; or
 
     (iv)  circumstances exist whereby a person or class of persons would be
           likely to have any claim or claims in respect of any oil and/or
           gas exploration, appraisal, development or production activities
           or any product or process of manufacture or materials used
           therein now or previously conducted, manufactured, sold or
           carried out by any past or present member of the Wider Aran Group
           which claim or claims would be likely to affect adversely any
           member of the Wider Aran Group;
 
       and any such matter is adverse to and material in the context of the
       Wider Aran Group;
 
   (h) any necessary exchange control consents or clearances required to
       implement the Offer having been received;
 
   (i) there being no provision of any agreement, arrangement, licence,
       permit, authorisation, royalty agreement or other instrument,
       including any joint venture agreement, to or of which any member of
       the Wider Aran Group or any partnership or company or other entity in
       which any member of the Wider Aran Group is interested (an
       "associate") is a party or has the benefit or by or to which any such
       member or associate or their assets may be bound, entitled or subject
       which, as a consequence of the Offer or the proposed acquisition by
       ARCO Irish Holdings of any Aran shares (including Aran shares
       represented by Aran ADSs) or control of Aran, or any part thereof,
       could or might result in:
 
     (i)   any monies borrowed by, or any other indebtedness, actual or
           contingent, of, any such member or associate (other than pursuant
           to the Supplemental Agreement dated 29 June 1994 relating to a
           Facility Agreement dated 27 February 1992, each made between
           certain Aran Group companies and certain banks and other parties
           as specific therein) being or becoming repayable or capable of
           being declared repayable immediately or earlier than the repayment
           date provided for in such arrangement, agreement or instrument or
           the ability of any such member or associate to borrow monies or
           incur any indebtedness being withdrawn or inhibited;
 
     (ii)  any such agreement, arrangement, licence, permit, authorisation,
           royalty agreement or instrument being terminated, revoked or
           modified or any obligation arising or any action being taken or
           arising thereunder;
 
     (iii) the interests or business of any such member or associate in or
           with any person, firm, company or body (or any arrangements
           relating to such interests or business) being terminated or
           modified or affected;
 
                                      18
<PAGE>
 
     (iv) any assets of any such member or associate being disposed of or
          charged otherwise than in the ordinary course of business;
 
     (v)  the creation of any mortgage, charge or other security interest
          over the whole or any part of the business, property or assets of
          any such member or associate or any such security, whenever
          arising or having arisen, becoming enforceable; or
 
     (vi) the value of any member or associate of the Wider Aran Group or
          its financial or trading position being adversely affected;
 
     and in any such case the result will be adverse to and material in the
     context of the Wider Aran Group taken as a whole;
 
   (j) no government or governmental, quasi-governmental, supranational,
       statutory or regulatory body, or any court, trade agency,
       association, institution or professional body or any other body or
       person whatsoever in any jurisdiction (including any foreign
       jurisdiction) having decided to take, instituted, implemented or
       threatened any action, proceedings, suit, investigation or enquiry
       (and in each case not having withdrawn such action, proceedings,
       suit, investigation or enquiry), or enacted, made or proposed any
       statute, regulation, decision or order (and in each case not having
       withdrawn the statute, regulation, decision or order) or taken any
       other steps which would or might:
 
     (i)   require or prevent the divestiture by any member of the ARCO Group
           or any member of the Wider Aran Group of all or any portion of
           their respective businesses, assets or property or impose any
           limitation on the ability of any of them to conduct their
           respective businesses and own any of their respective assets or
           property;
 
     (ii)  make the Offer or the acquisition of any Aran shares or control
           of Aran by any member of the ARCO Group void, illegal, and/or
           unenforceable, or otherwise restrain, restrict, prohibit, delay
           or otherwise interfere with the implementation thereof, or impose
           additional conditions or obligations with respect thereto;
 
     (iii) require any member of the ARCO Group or any member of the Wider
           Aran Group to offer to acquire any shares in any member of the
           Wider Aran Group owned by any third party;
 
     (iv)  impose any limitation on the ability of any member of the ARCO
           Group to acquire or hold or to exercise effectively any rights of
           ownership of shares in Aran or on the ability of Aran or any
           other member of the Wider Aran Group or any member of the ARCO
           Group to hold or exercise effectively any rights of ownership of
           shares in any member of the Wider Aran Group held or owned by it;
           or
 
     (v)   otherwise adversely affect the business, profits or prospects of
           any member of the ARCO Group or of the Wider Aran Group;
 
       and all applicable waiting and other time periods during which any
       such government, governmental, quasi-governmental, supranational,
       statutory or regulatory body, court, trade agency, association,
       institution or professional body or person or body could institute any
       such action, proceedings, suit, investigation or enquiry having
       expired, lapsed or been terminated;
 
   (k) all authorisations, orders, recognitions, grants, consents, licences,
       confirmations, clearances, permissions and approvals necessary or
       appropriate for or in respect of the Offer or proposed acquisition of
       any shares in, or control of, Aran by ARCO Irish Holdings having been
       obtained in terms and in a form satisfactory to ARCO Irish Holdings
       from all appropriate governments, governmental, quasi-governmental,
       supranational, statutory or regulatory bodies or courts, trade
       agencies, associations, institutions or professional bodies or from
       any bodies or persons whatsoever in any jurisdiction (including any
       foreign jurisdiction) with whom any member of the Aran Group has
       entered into contractual arrangements and such authorisations,
       orders, recognitions, grants, consents, licences, confirmations,
       clearances, permissions and approvals together with all
       authorisations, orders, recognitions, grants, licences,
       confirmations, clearances, permissions and approvals necessary or
       appropriate to carry on the business of any member of the Aran Group
       remaining in full force and effect at the time at which the Offer
       becomes otherwise unconditional and all necessary filings having been
       made for such purposes and all appropriate waiting periods under the
       US HSR Act and any other applicable legislation or regulations in any
       jurisdiction having expired or been terminated and there being no
       intimation of any intention to revoke or not to renew any of the same
       and all necessary statutory or regulatory obligations in any
       jurisdiction having been complied with;
 
                                      19
<PAGE>
 
   (l) except as publicly announced by Aran prior to 17 August 1995, no
       member of the Wider Aran Group having, since 31 December 1994:
 
     (i)    save as between Aran and wholly owned subsidiaries of Aran or upon
            the exercise of the right to subscribe for Aran shares pursuant to
            the exercise of options under any of the Aran share option schemes
            or pursuant to intra-group transactions on or prior to the date
            hereof, issued, authorised or proposed the issue of additional
            shares of any class;
 
     (ii)   save as between Aran and wholly owned subsidiaries of Aran,
            issued or authorised or proposed the issue of or granted
            securities convertible into, shares or rights, warrants or
            options to subscribe for, or acquire, any such shares or
            convertible securities;
 
     (iii)  save as between Aran and wholly owned subsidiaries of Aran,
            merged with any body corporate or acquired or disposed of or
            transferred, mortgaged or charged or created any security
            interest over any assets or any rights, title or interest in any
            asset (including shares and trade investments) or authorised or
            proposed or announced any intention to propose any merger,
            demerger, acquisition, disposal, transfer, mortgage, charge or
            security interest other than in the ordinary course of business;
 
     (iv)   leased or in any other manner restricted or terminated its
            control over or access to any of its material assets, whether for
            valuable consideration or otherwise, including (without
            limitation) by farm-out, of any of its right, title or interest
            under any licence or operating concession or other agreement
            concerning the exploration for, or the ownership, exploitation,
            extraction, development, production, operation or abandonment of,
            any oil, natural gas or other hydrocarbon deposit or reservoir or
            otherwise by granting rights to any person outside the Aran Group
            (or terminating any of its own rights) over or in relation to its
            oil, natural gas or other hydrocarbon interests or assets
            (whether or not in the ordinary course of its business);
 
     (v)    save as between Aran and wholly owned subsidiaries of Aran,
            authorised or proposed or announced an intention to propose any
            change in its share or loan capital or to purchase any of its own
            shares;
 
     (vi)   save as between Aran and wholly owned subsidiaries of Aran,
            issued, authorised or proposed the issue of any debentures or
            incurred or increased any indebtedness or become subject to any
            contingent liability which is material in the context of the
            Wider Aran Group taken as a whole;
 
     (vii)  entered into any contract, reconstruction, amalgamation,
            commitment or other transaction or arrangement otherwise than in
            the ordinary course of business or entered into or changed the
            terms of any contract with any director or senior executive of
            any member of the Wider Aran Group;
 
     (viii) entered into any contract or commitment (whether in respect of
            capital expenditure or otherwise) which is of a long term or
            unusual nature or which involves or could involve an obligation
            of a nature or magnitude in either case which is material in
            the context of the Wider Aran Group taken as a whole;
 
     (ix)   declared, paid, made or proposed to declare, pay or make, any
            bonus, dividend or other distribution;
 
     (x)    in the case of Aran, proposed any voluntary winding up;
 
     (xi)   waived any material claim; or
 
     (xii)  entered into any contract, commitment or agreement with respect
            to any of the transactions or events referred to in this sub-
            paragraph (l) or announced any intention or passed any
            resolution to do so;
 
   (m) since 31 December 1994 and save as disclosed in the accounts of Aran
       for the year then ended, (the "published results") or as publicly
       announced by Aran prior to 17 August 1995:
 
     (i)   no adverse change having occurred in the business, financial or
           trading position or profits or assets or prospects of any member
           of the Wider Aran Group;
 
     (ii)  no contingent liability having arisen which would or might
           adversely affect any member of the Wider Aran Group; and
 
     (iii) no litigation, arbitration proceedings, prosecution or other
           legal proceedings having been instituted or threatened by or
           against or remaining outstanding against any member of the Wider
           Aran Group which is adverse to and material in the context of
           the Wider Aran Group taken as a whole; and
 
   (n) ARCO Irish Holdings not having discovered:
 
     (i)   that any financial or business information which has been publicly
           disclosed at any time by any member of the Aran Group either
           contains a misrepresentation of fact or omits to state a fact
 
                                      20
<PAGE>
 
          necessary to make the information contained therein not misleading,
          which misrepresentation or omission was not corrected by subsequent
          public announcement made on or before 17 August 1995 and is
          material in the context of the Offer; or
 
     (ii) that any member of the Wider Aran Group which is not a subsidiary
          of Aran is subject to any liability (contingent or otherwise)
          which is not disclosed in the published results and which has a
          material adverse effect on the Wider Aran Group taken as a whole.
 
   In this Appendix 1 a reference to a public announcement by Aran shall mean
   an announcement delivered by or on behalf of Aran to the Company
   Announcements Office of the Irish Stock Exchange and the London Stock
   Exchange and publicly announced shall be construed accordingly.
 
   ARCO Irish Holdings reserves the right to waive (where possible), in whole
   or in part, all or any of conditions (b) to (n) inclusive. The Offer will
   lapse unless all conditions relating to the Offer have been fulfilled or,
   if capable of waiver, waived on or before 3.00 p.m. (Dublin and London
   time), 10.00 a.m. (New York City time) on 23 September 1995 or such later
   date as ARCO Irish Holdings may decide and in any event on or before
   midnight (Dublin and London time), 8.00 p.m. (New York City time) on 24
   October 1995 or on such later date as the Panel may agree. ARCO Irish
   Holdings shall be under no obligation to waive or treat as satisfied any
   of conditions (b) to (n) inclusive by a date earlier than the latest date
   specified above for the satisfaction thereof notwithstanding that the
   other conditions of the Offer may at such earlier date have been waived or
   fulfilled and that there are at such earlier date no circumstances
   indicating that any such conditions may not be capable of fulfilment.
 
   ARCO Irish Holdings intends, if appropriate, to seek the Panel's approval
   to extend the date by which conditions (b) to (n) inclusive must be
   satisfied or waived to not later than 14 November 1995 (or such later date
   as the Panel may agree). Unless otherwise determined by ARCO Irish
   Holdings (with the consent of the Panel), the Offer will lapse unless at
   the latest time and date at which the Offer shall be terminated or expire
   (the closing date) the Acceptance Condition is or remains satisfied by
   reference to acceptances and purchases permitted to be counted towards
   fulfilling the Acceptance Condition (other than acceptances withdrawn on
   or before the closing date), and subject to the consent of the Panel, by
   reference to the issued share capital of Aran as at the first time and
   date on which the Acceptance Condition is satisfied.
 
   If ARCO Irish Holdings is required by the Panel to make an offer for Aran
   securities under the provisions of Rule 9 of the City Code, ARCO Irish
   Holdings may make such alterations to the conditions, including the
   Acceptance Condition above, as are necessary to comply with the provisions
   of that Rule.
 
   The Offer will lapse if the Acquisition is referred to the UK Monopolies
   and Mergers Commission before 3.00 p.m. (Dublin and London time), 10.00
   a.m. (New York City time) on 23 September 1995 or the date on which the
   Offer becomes or is declared unconditional as to acceptances, whichever is
   the later.
 
   If the Minister for Enterprise and Employment of Ireland makes an order
   under Section 9 of the Mergers Act prohibiting the Acquisition or
   prohibiting the Acquisition except on conditions specified in such order,
   the Offer will lapse unless, in the case of an order prohibiting the
   Acquisition except on conditions specified in such order, ARCO Irish
   Holdings, in its absolute discretion, shall decide to accept such
   conditions.
 
   If the Offer lapses, the Offer will cease to be capable of further
   acceptance and accepting Aran securityholders and ARCO Irish Holdings will
   cease to be bound by Acceptance Forms submitted before the time when the
   Offer lapses.
 
PART B--FURTHER TERMS OF THE OFFER
 
1. Acceptance period
 
   (a) The Offer will initially be open for acceptance until 3.00 p.m.
       (Dublin and London time), 10.00 a.m. (New York City time) on 23
       September 1995. Although no revision is envisaged, if the Offer is
       revised it will remain open for acceptance for a period of at least 14
       days from the date of despatching the revised Offer document to Aran
       securityholders. Except with the consent of the Panel, no revision of
       the Offer may be made or posted after 10 October 1995, or if later,
       the date falling 14 days prior to the last date on which the Offer can
       become unconditional.
 
   (b) The Offer, whether revised or not, shall not (except with the consent
       of the Panel) be capable of becoming unconditional after midnight
       (Dublin and London time), 8.00 p.m. (New York City time) on 24 October
       1995 (or any earlier time and/or date announced by ARCO Irish Holdings
       as the date beyond which ARCO Irish Holdings has stated that the Offer
       will not be extended and in respect of which it has not withdrawn
 
                                      21
<PAGE>
 
       that statement) nor of being kept open after that time unless it has
       previously become unconditional, provided that ARCO Irish Holdings
       reserves the right, with the permission of the Panel, to extend the
       time for the Offer to become unconditional to a later time or times
       and/or date(s). ARCO Irish Holdings intends, if appropriate, to seek
       the Panel's approval to extend this date to not later than 14 November
       1995 (or such later date as the Panel may agree) for the satisfaction
       (or waiver) of conditions (b) to (n). ARCO Irish Holdings may not, for
       the purpose of determining whether the Acceptance Condition has been
       satisfied, take into account acceptances received or purchases of
       shares made after 1.00 p.m. (Dublin and London time), 9.00 a.m. (New
       York City time) on 24 October 1995 (or any earlier time and/or date
       announced (and not withdrawn) by ARCO Irish Holdings as the date beyond
       which the Offer will not be extended) or such later time(s) and/or
       date(s) as ARCO Irish Holdings, with the permission of the Panel, may
       determine.
 
   (c) If the Offer becomes unconditional, it will remain open for acceptance
       for not less than 14 days from the date on which it would otherwise
       have expired. If the Offer has become unconditional and it is stated
       that the Offer will remain open until further notice, not less than 14
       days notice in writing will be given prior to the expiry of the Offer.
 
   (d) The Offer may not be revised or amended after it has become
       unconditional. However, ARCO Irish Holdings expressly reserves the
       right, at any time or from time to time, to extend the Offer one or
       more times after it has become unconditional and, in such event, will
       give oral or written notice of such extension to the Irish Receiving
       Agent, the UK Receiving Agent and the US Depositary and make a public
       announcement of such extension in the manner described in paragraph 5
       (Announcements); provided, however, that not less than 14 days notice
       will be given prior to the expiry of the Offer in the event of it
       being so extended.
 
   (e) If a competitive situation arises after a no increase and/or no
       extension statement has been made in relation to the Offer, ARCO Irish
       Holdings may, if it specifically reserves the right to do so at the
       time such statement is made, or otherwise with the consent of the
       Panel, withdraw such statement if it announces such withdrawal within
       four business days (or such later period as the Panel may agree) after
       the announcement of the competing offer and notifies Aran
       securityholders in writing thereof. ARCO Irish Holdings may, if it has
       reserved the right to do so, choose not to be bound by the terms of a
       no increase or no extension statement if it would otherwise prevent
       the posting of an increased or improved Offer which is recommended for
       acceptance by the board of Aran, or in other circumstances permitted
       by the Panel.
 
   (f) For the purpose of determining whether the Acceptance Condition has
       been fulfilled, ARCO Irish Holdings shall not be bound (unless
       otherwise required by the Panel) to take into account any Aran
       securities which have been unconditionally allotted or issued after 25
       August 1995 but before such determination takes place unless Aran has
       notified the UK Receiving Agent, on behalf of ARCO Irish Holdings, in
       writing of the relevant details of such issue or allotment prior
       thereto. Telex or facsimile transmission or copies will not constitute
       notification in writing for this purpose.
 
2. Defective Acceptances
 
Subject to the provisions of the City Code, ARCO Irish Holdings and
Rothschilds reserve the absolute right to treat an acceptance of the Offer as
valid even if such acceptance is not entirely in order or is not accompanied
by the relevant documents or is otherwise received at any place or places
otherwise than as set out in this document or the Acceptance Forms or
otherwise to waive any defect or irregularity in the acceptance of the Offer
in respect of any Aran securities. None of ARCO Irish Holdings, Rothschilds,
the Irish Receiving Agent, the UK Receiving Agent, the US Depositary, the US
Dealer Manager or any other person will be under any duty to give notification
of any defects or irregularities in any acceptance of the Offer or incur any
liability for failure to give any such notification.
 
3. Form of Acceptance for Aran Shareholders
 
Each Aran shareholder by whom, or on whose behalf, a Form of Acceptance is
executed irrevocably undertakes, represents, warrants and agrees to and with
ARCO Irish Holdings and Rothschilds (so as to bind such shareholder and such
shareholder's personal representatives, heirs, successors and assigns) to the
following effect:
 
   (a) that the execution of a Form of Acceptance constitutes:
 
     (i) an acceptance of the Offer in respect of the number of Aran shares
         inserted or deemed to be inserted in Box 1 of the Form of
         Acceptance; and
 
                                      22
<PAGE>
 
     (ii) an undertaking to execute any further documents and give any
          further assurances which may be required to enable ARCO Irish
          Holdings to obtain the full benefit of this paragraph 3 and/or to
          perfect any of the authorities expressed to be given hereunder,
 
     in each case on and subject to the terms and conditions set out or
     referred to in this document and the Form of Acceptance and an
     undertaking that, subject only to the rights of withdrawal set out in
     paragraph 6 of Part B of this Appendix 1 (Rights of withdrawal), each
     such acceptance and election shall be irrevocable;
 
   (b) that such holder is entitled to sell and transfer the beneficial
       ownership of the Aran shares in respect of which the Offer is
       accepted or deemed to be accepted and that such Aran shares are sold
       fully paid and free from all liens, equitable interests, charges, and
       encumbrances and together with all rights attaching thereto since
       (and including) 21 August 1995 including voting rights and the right
       to all dividends and other distributions declared, made or paid on or
       after 21 August 1995;
 
   (c) that the execution of the Form of Acceptance constitutes, subject to
       the Offer becoming unconditional, the irrevocable appointment of each
       of ARCO Irish Holdings and Rothschilds and any of their respective
       directors and agents as such Aran shareholders attorney and/or agent
       (the "attorney"), and an irrevocable instruction to the attorney
       within nine months of the Offer becoming unconditional to complete
       and execute all or any form(s) of transfer and/or other document(s)
       at the discretion of the attorney in relation to the Aran shares
       referred to in paragraph 3(a) in respect of which an accepting Aran
       shareholder has not validly withdrawn his or her acceptance in favour
       of ARCO Irish Holdings or such other person or persons as ARCO Irish
       Holdings may direct and to deliver such form(s) of transfer and/or
       other document(s) at the discretion of the attorney together with the
       share certificate(s) and/or other document(s) of title relating to
       such Aran shares for registration and to do all such other acts and
       things as may in the opinion of the attorney be necessary or
       expedient for the purposes of, or in connection with, the acceptance
       of the Offer to vest in ARCO Irish Holdings or its nominee(s) the
       title to the Aran shares as aforesaid;
 
   (d) that such Aran shareholder (i) has not received or sent copies of
       this document or any Form of Acceptance or any related documents in,
       into or from Australia, Canada or Japan; (ii) is accepting the Offer
       from outside Australia, Canada and Japan; and (iii) is not an agent
       or fiduciary acting on a non-discretionary basis for a principal,
       unless such agent or fiduciary is an authorised employee of such
       principal or such principal has given any instructions with respect
       to the Offer from outside Australia, Canada and Japan;
 
   (e) that the execution of the Form of Acceptance constitutes, subject to
       the Offer becoming unconditional and to an accepting Aran shareholder
       not having validly withdrawn his acceptance, an irrevocable authority
       and request:
 
     (i)  to Aran or its agents to procure the registration of the transfer
          of the Aran shares to which such Form of Acceptance relates
          pursuant to the Offer and the delivery of the share certificate(s)
          and/or other document(s) of title in respect thereof to ARCO Irish
          Holdings or as it may direct; and
 
     (ii) subject to the provisions of paragraph 9 of Part B of this
          Appendix 1 (Overseas holders of Aran shares and Aran ADSs), to
          ARCO Irish Holdings or its agents to procure the despatch by post
          (or by such other method as may be approved by the Panel) of a
          cheque for the cash consideration to which an accepting Aran
          shareholder becomes entitled pursuant to his or her acceptance of
          the Offer, at the risk of such Aran shareholder to the person
          whose name and address is set out in Box 4 on the Form of
          Acceptance or, if none is set out, to the first-named holder at
          his or her registered address;
 
   (f) that the execution of the Form of Acceptance constitutes a separate
       authority to each of ARCO Irish Holdings and Rothschilds and any of
       their respective directors and agents in the terms of paragraph 7 of
       Part B of this Appendix 1 (Revised Offer and reduction of the
       Acceptance Condition);
 
   (g) that, after the Offer has become unconditional (or if the Offer will
       become unconditional or lapse immediately upon the outcome of the
       resolution in question or in such other circumstances as ARCO Irish
       Holdings may request and the Panel may permit):
 
     (i) ARCO Irish Holdings or its agents shall be entitled to direct the
         exercise of any votes attaching to any Aran shares in respect of
         which the Offer has been accepted or is deemed to have been
         accepted (the "Acceptance Shares") and any or all other rights and
         privileges (including the right to requisition the convening of a
         general meeting or separate class meeting of Aran) attaching to
         any Acceptance Shares;
 
                                      23
<PAGE>
 
     (ii) the execution of the Form of Acceptance by an Aran shareholder
          shall constitute in respect of the Acceptance Shares:
 
           (a) an authority to Aran or its agents from such Aran shareholder
               to send any notice, circular, warrant, document or other
               communication which may be required to be sent to him or her as
               a Aran shareholder to ARCO Irish Holdings at its principal
               office;
 
           (b) an authority to ARCO Irish Holdings or any director of ARCO
               Irish Holdings or any person appointed by such person for such
               purpose to sign any consent to short notice of a general
               meeting or separate class meeting on his or her behalf and/or
               execute a form of proxy in respect of the Acceptance Shares
               appointing any person nominated by ARCO Irish Holdings to
               attend general meetings and separate class meetings of Aran and
               any adjournment thereof and to exercise the votes attaching to
               the Acceptance Shares on his or her behalf, such votes to be
               cast (where relevant) so far as possible to satisfy or to
               assist directly or indirectly in satisfying any outstanding
               condition of the Offer; and
 
           (c) the agreement of such Aran shareholder not to exercise any of
               such rights without the consent of ARCO Irish Holdings and the
               irrevocable undertaking of such shareholder not to appoint a
               proxy for or to attend any such general meetings or separate
               class meetings in respect of the Acceptance Shares;
 
   (h) that he or she will deliver to the Irish Receiving Agent, the UK
       Receiving Agent or the US Depositary, as appropriate, at the relevant
       address set out on the back page of this document, his or her share
       certificate(s) and/or other document(s) of title in respect of the
       Aran shares referred to in paragraph (a) of this paragraph 3, or an
       indemnity acceptable to ARCO Irish Holdings in lieu thereof, as soon
       as possible and in any event within six months of the Offer becoming
       unconditional;
 
   (i) that the terms and conditions of the Offer contained in this document
       shall be incorporated in and form part of the Form of Acceptance,
       which shall be read and construed accordingly;
 
   (j) that he or she agrees to ratify each and every act or thing which may
       be done or effected by ARCO Irish Holdings or Rothschilds or any of
       their respective directors or agents or Aran or its agents, as the
       case may be, in the proper exercise of any of its or his or her
       powers and/or authorities hereunder;
 
   (k) that if he or she accepts the Offer and does not validly withdraw
       such acceptance, he or she will do all such acts and things as shall
       be necessary or expedient to vest in ARCO Irish Holdings or its
       nominee(s) the title to the Aran shares aforesaid;
 
   (l) that in consideration of ARCO Irish Holdings making the benefit of
       any revised Offer available to him or her as stated in paragraph 7 of
       Part B of Appendix 1 (Revised Offer and reduction of the Acceptance
       Condition), the deemed acceptances, elections and authorities
       referred to in such paragraph shall, subject to the rights of
       withdrawal set out in paragraph 6 of Part B of Appendix 1 (Rights of
       withdrawal), be irrevocable; and
 
   (m) that if any provision of Part B of this Appendix 1 shall be
       unenforceable or invalid or shall not operate so as to afford ARCO
       Irish Holdings or Rothschilds the benefit of an authority expressed
       to be given therein, he or she shall with all practicable speed do
       all such acts and things and execute all such documents that may be
       required to enable ARCO Irish Holdings or Rothschilds to secure the
       full benefits of Part B of this Appendix 1.
 
References in this paragraph 3 to an Aran shareholder shall include references
to the person or persons executing a Form of Acceptance and in the event of
more than one person executing a Form of Acceptance the provisions of this
Part B shall apply to them jointly and to each of them.
 
A holder of Aran shares tendering to First Chicago Trust Company of New York
may be subject to US back-up withholding on cash payments received in exchange
for his or her shares. Further information regarding back-up withholding is
set out in paragraph 12 of Appendix 4.
 
4. Acceptance Procedures for Holders of Aran ADSs
 
(a) Valid acceptance
 
For a holder of Aran ADSs validly to accept the Offer either:
 
   (i) a properly completed and duly executed Letter of Transmittal (or
       facsimile thereof), together with any required signature guarantees
       and any other required documents, must be received by the US
       Depositary at one of its addresses set out on page 63 of this
       document, and the Aran ADRs evidencing such Aran ADSs must be
       received by the US Depositary at one of such addresses or delivered
       pursuant to the procedures for book-entry transfer set out in
       paragraph (c) below (and a confirmation of receipt of such transfer
       received by the US Depositary); or
 
                                      24
<PAGE>
 
   (ii) such holder must comply with the guaranteed delivery procedures set
        out in paragraph (g) below.
 
   Delivery of the Letter of Transmittal, Aran ADRs evidencing tendered Aran
   ADSs (or book-entry transfer of such Aran ADSs) and any other required
   documents to the US Depositary by an Aran ADS holder will be deemed
   (without any further action by the US Depositary) to constitute
   acceptance of the Offer by such Aran ADS holder in respect of such
   holder's Aran ADSs, subject to the terms and conditions set out in this
   document and the Letter of Transmittal. The acceptance of the Offer by an
   Aran ADS holder pursuant to the procedures described above, subject to
   the withdrawal rights described below, will constitute a binding
   agreement between such Aran ADS holder and ARCO Irish Holdings upon the
   terms and subject to the conditions of the Offer. If acceptance has been
   made in respect of a Aran ADS then a separate acceptance in respect of
   the Aran shares represented by such Aran ADS may not be made.
 
(b) The Letter of Transmittal
 
By executing the Letter of Transmittal (together with any signature
guarantees) as set out above, the accepting Aran ADS holder agrees to the
authorisations set out therein, including, without limitation, that effective
from and after the date thereof or, if later, the date on which the Offer
becomes unconditional (or if the Offer will become unconditional or lapse
immediately upon the outcome of the resolution in question or in such other
circumstances as ARCO Irish Holdings may request and the Panel may permit):
 
   (i)  ARCO Irish Holdings or its agents shall be entitled to direct the
        exercise of any votes attaching to the Aran shares represented by any
        Aran ADSs in respect of which the Offer has been accepted or is
        deemed to have been accepted (the "Accepted ADSs") and any or all
        other rights and privileges attaching to such Aran ADSs, including
        any right to requisition the convening of a general or separate class
        meeting of Aran; and
 
   (ii) the execution of the Letter of Transmittal by a holder of Aran ADSs
        (together with any signature guarantees) and its delivery to the US
        Depositary shall constitute in respect of Accepted ADSs:
 
     (a) an authority to Aran or its agents from the holder of Accepted
         ADSs to send any notice, circular, warrant, document or other
         communication that may be required to be sent to him or her as an
         Aran ADS holder to ARCO Irish Holdings at its principal office;
 
     (b) an authority to ARCO Irish Holdings or any director of ARCO Irish
         Holdings or any person appointed by such person for such purpose
         to sign any consent to short notice of a general meeting or
         separate class meeting on behalf of the holder of Accepted ADSs
         and/or to execute a form of proxy in respect of the Accepted ADSs
         appointing any person nominated by ARCO Irish Holdings to attend
         general meetings and separate class meetings of Aran and any
         adjournment thereof and to exercise the votes attaching to the
         Aran shares represented by such Accepted ADSs on his or her
         behalf, such votes to be cast (where relevant) so far as possible
         to satisfy or to assist directly or indirectly in satisfying any
         outstanding condition of the Offer;
 
     (c) the agreement of such holder of Accepted ADSs not to exercise any
         of such rights without the consent of ARCO Irish Holdings and the
         irrevocable undertaking of such holder of Accepted ADSs not to
         appoint a proxy for or to attend any such general meetings or
         separate class meetings in respect of the Accepted ADSs;
 
     (d) confirmation that such Aran securityholder (i) has not received or
         sent copies of this document or any Letter of Transmittal or any
         related documents in, into or from Australia, Canada or Japan;
         (ii) is accepting the Offer from outside Australia, Canada and
         Japan; and (iii) is not an agent or fiduciary acting on a non-
         discretionary basis for a principal, unless such agent or
         fiduciary is an authorised employee of such principal or such
         principal has given any instructions with respect to the Offer
         from outside Australia, Canada and Japan; and
 
     (e) confirmation that such Aran securityholder is entitled to sell and
         transfer the beneficial ownership of the Accepted ADSs and that
         such Accepted ADSs are sold fully paid and free from all liens,
         equitable interests, charges, and encumbrances and together with
         all rights attaching thereto since (and including) 21 August 1995
         including voting rights and the right to all dividends and other
         distributions declared, made or paid on or after 21 August 1995;
         and
 
   (iii) the execution of the Letter of Transmittal (together with any
         signature guarantees) and its delivery to the US Depositary shall
         constitute an authority to any director of ARCO Irish Holdings or
         Rothschilds and to ARCO Irish Holdings or Rothschilds and/or their
         respective agents in accordance with the terms of paragraph 7 of
         Part B of this Appendix 1 (Revised offer and reduction of the
         Acceptance Condition).
 
                                      25
<PAGE>
 
   REFERENCES IN THIS PARAGRAPH 4 TO AN ARAN SECURITYHOLDER SHALL INCLUDE
   REFERENCES TO THE PERSON OR PERSONS EXECUTING A LETTER OF TRANSMITTAL AND
   IN THE EVENT OF MORE THAN ONE PERSON EXECUTING A LETTER OF TRANSMITTAL
   THE PROVISIONS OF THIS PART B SHALL APPLY TO THEM JOINTLY AND TO EACH OF
   THEM.
 
(c) Book-Entry Transfer Facilities
 
The US Depositary will establish an account at the Book-Entry Transfer
Facilities with respect to the Aran ADSs held in book-entry form for the
purposes of the Offer within two US Business Days after the date of despatch
of this document. Any financial institution that is a participant in any of
the Book-Entry Transfer Facilities' systems may make book-entry delivery of
Aran ADSs by causing a Book-Entry Transfer Facility to transfer such Aran ADSs
into the US Depositary's account at such Book-Entry Transfer Facility in
accordance with that Book-Entry Transfer Facility's procedure for such
transfer.
 
Although delivery of Aran ADSs may be effected through book-entry transfer
into the US Depositary's account at a Book-Entry Transfer Facility (i) the
Letter of Transmittal (or facsimile thereof), properly completed and duly
executed, together with any required signature guarantees and any other
required documents, must in any case be transmitted to, and received by, the
US Depositary at one of its addresses set out on page 63 of this document
before such delivery of Aran ADSs will be counted as a valid acceptance for
the purposes of the Acceptance Condition or such Aran ADSs will be purchased
in the event that the Offer becomes unconditional, or (ii) such holder must
comply with the guaranteed delivery procedures set out in paragraph (g) below.
DELIVERY OF DOCUMENTS TO A BOOK-ENTRY TRANSFER FACILITY IN ACCORDANCE WITH
SUCH BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO
THE US DEPOSITARY.
 
(d) Method of delivery
 
The method of delivery of Aran ADSs and all other required documents is at the
option and risk of the accepting Aran ADS holder. If delivery is by mail,
registered mail with return receipt requested, properly insured, is
recommended. Delivery should be effected as soon as possible but in any event
so that documents (and, in the case of a book-entry transfer, a confirmation
of receipt of such transfer by the US Depositary) are received by not later
than 10.00 a.m. (New York City time), 3.00 p.m. (Dublin and London time) on 23
September 1995. In all cases, sufficient time should be allowed to ensure
timely delivery. No acknowledgement of receipt of documents will be given.
 
(e) Signature guarantees
 
No signature guarantee is required on the Letter of Transmittal if (i) the
Letter of Transmittal is signed by the registered holder of the Aran ADSs in
respect of which the Offer is being accepted and such registered holder has
not completed either the Box entitled "Special Delivery Instructions" or the
Box entitled "Special Payment Instructions" on the Letter of Transmittal or
(ii) such Aran ADSs are accepted for the account of an Eligible Institution.
In all other cases, all signatures on Letters of Transmittal must be
guaranteed by an Eligible Institution. See Instructions 1 and 5 to the Letter
of Transmittal.
 
If the Aran ADSs are registered in the name of a person other than the
signatory of the Letter of Transmittal then the Aran ADRs evidencing the Aran
ADSs in respect of which the Offer is being accepted must be endorsed or
accompanied by appropriate stock powers, signed exactly as the name or names
of the registered owner or owners appear on the Aran ADRs, with the signatures
on such Aran ADRs or stock powers guaranteed as aforesaid. See Instruction 5
to the Letter of Transmittal.
 
(f) Partial acceptances
 
If the Offer is to be accepted in respect of less than all of the Aran ADSs
evidenced by any Aran ADRs delivered to the US Depositary then the holder
thereof should so indicate in the Letter of Transmittal by filling in the
number of Aran ADSs in respect of which the Offer is being accepted in the Box
entitled "Number of Accepting Aran ADSs". In such case, in the event of the
Offer becoming unconditional, a new Aran ADR for the remainder of the Aran
ADSs (in respect of which the Offer was not accepted) represented by the old
Aran ADR will be sent to the registered holder (or delivered to the person
signing the Letter of Transmittal or in accordance with such person's
instructions as such person properly indicates thereon) as promptly as
practicable following the date on which the Aran ADSs in respect of which the
Offer has been accepted are purchased.
 
THE OFFER WILL BE DEEMED TO HAVE BEEN ACCEPTED IN RESPECT OF ALL ARAN ADSS
EVIDENCED BY ARAN ADRS DELIVERED TO THE US DEPOSITARY UNLESS OTHERWISE
INDICATED. See Instruction 4 to the Letter of Transmittal. In the case of
partial acceptances, Aran ADSs in respect of which the Offer was not accepted
will not be reissued to a person other than the registered holder of the
related ADR.
 
                                      26
<PAGE>
 
(g) Guaranteed delivery procedures
 
If a holder of Aran ADSs wishes to accept the Offer and the Aran ADRs
evidencing such Aran ADSs are not immediately available or the procedures for
book-entry transfer cannot be completed on a timely basis, or if time will not
permit all required documents to reach the US Depositary prior to the expiry
of the Offer, such holder's acceptance of the Offer may nevertheless be
effected if all of the following conditions are satisfied (being the
guaranteed delivery procedures):
 
   (i)   acceptance is made by or through an Eligible Institution;
 
   (ii)  a properly completed and duly executed Notice of Guaranteed Delivery
         substantially in the form provided by ARCO Irish Holdings is
         received by the US Depositary, as provided below, prior to the Offer
         having expired; and
 
   (iii) the Aran ADRs evidencing the Aran ADSs in respect of which the
         Offer is being accepted (or, in the case of Aran ADSs held in book-
         entry form, timely confirmation of the book-entry transfer of such
         Aran ADSs into the US Depositary's account at a Book-Entry Transfer
         Facility as described above) together with a properly completed and
         duly executed Letter of Transmittal (or facsimile thereof) with any
         required signature guarantees and any other documents required by
         the Letter of Transmittal, are received by the US Depositary within
         three trading days after the date of execution of such Notice of
         Guaranteed Delivery. For these purposes, a "trading day" is any day
         on which NASDAQ is open for business.
 
The Notice of Guaranteed Delivery may be delivered by hand to the US
Depositary or transmitted by facsimile transmission or mailed to the US
Depositary and must include a signature guarantee by an Eligible Institution
in the form set out in such Notice of Guaranteed Delivery.
 
RECEIPT OF A NOTICE OF GUARANTEED DELIVERY WILL NOT BE TREATED AS A VALID
ACCEPTANCE FOR THE PURPOSE OF SATISFYING THE ACCEPTANCE CONDITION. TO BE
COUNTED TOWARDS SATISFACTION OF THIS CONDITION, PRIOR TO THE OFFER HAVING
EXPIRED THE ARAN ADRs EVIDENCING ARAN ADSs REFERRED TO IN THE NOTICE OF
GUARANTEED DELIVERY MUST HAVE BEEN RECEIVED BY THE US DEPOSITARY OR, IN THE
CASE OF ARAN ADSs HELD IN BOOK-ENTRY FORM, TIMELY CONFIRMATION OF A BOOK-ENTRY
TRANSFER OF SUCH ARAN ADSs INTO THE US DEPOSITARY'S ACCOUNT AT A BOOK-ENTRY
TRANSFER FACILITY PURSUANT TO THE PROCEDURES SET OUT ABOVE MUST HAVE BEEN
RECEIVED BY THE US DEPOSITARY, IN EITHER CASE, TOGETHER WITH A DULY EXECUTED
LETTER OF TRANSMITTAL (OR FACSIMILE THEREOF) WITH ANY REQUIRED SIGNATURE
GUARANTEES AND ANY OTHER REQUIRED DOCUMENTS.
 
(h) US back-up withholding
 
A holder of Aran securities tendering to First Chicago Trust Company of New
York may be subject to US back-up withholding on cash payments received in
exchange for his or her securities. Further information regarding back-up
withholding is set out in paragraph 12 of Appendix 4.
 
5. Announcements
 
(a) Without prejudice to paragraph 6 below (Rights of withdrawal), by 8.30
    a.m. (Dublin and London time) in Ireland and the UK and 8.30 a.m (New York
    City time) in the US on the business day (the "relevant day") next
    following the day on which the Offer is due to expire or becomes
    unconditional or is revised or extended, ARCO Irish Holdings will make an
    appropriate announcement and simultaneously inform the Irish Stock
    Exchange, the London Stock Exchange and the Dow Jones News Service as
    appropriate. Such announcement will (unless otherwise permitted by the
    Panel) also state (as nearly as practicable) the total number of Aran
    shares (including Aran shares represented by Aran ADSs) and rights over
    such Aran shares:
 
   (i)   for which acceptances of the Offer have been received and not validly
         withdrawn (showing the extent, if any, to which such acceptances have
         been received from persons deemed to be acting in concert with ARCO
         Irish Holdings for the purposes of the Offer);
 
   (ii)  acquired or agreed to be acquired by or on behalf of ARCO Irish
         Holdings or persons acting in concert with ARCO Irish Holdings for
         the purposes of the Offer during the Offer period; and
 
   (iii) held by or on behalf of ARCO Irish Holdings or by persons deemed to
         be acting in concert with ARCO Irish Holdings prior to the Offer
         period,
 
                                      27
<PAGE>
 
    and will specify the percentage of Aran shares represented by each of
    these figures. Any decision to extend the time and/or date by which the
    Acceptance Condition has to be fulfilled may be made at any time up to,
    and will be announced not later than, 8.30 a.m. (Dublin and London time)
    in Ireland and the UK and 8.30 a.m. (New York City time) in the US on the
    relevant day and the announcement will state the next expiry date (unless
    the Offer is then unconditional, in which case a statement may instead be
    made that the Offer will remain open until further notice). In computing
    the number of Aran shares represented by acceptances and/or purchases,
    there may be included or excluded for announcement purposes acceptances
    and purchases not in all respects in order or subject to verification
    provided that such acceptances or purchases shall not be included unless
    they could be counted towards fulfilling the Acceptance Condition in
    accordance with paragraph 1(b) (Acceptance period) of this Part B.
 
(b) In this Appendix 1, references to the making of an announcement by ARCO
    Irish Holdings include the release of an announcement to the press by
    public relations consultants or by Rothschilds on behalf of ARCO Irish
    Holdings and the delivery by telephone, telex or facsimile or other
    electronic transmission of an announcement to the Irish Stock Exchange,
    the London Stock Exchange and telephone or facsimile transmission of such
    announcement to the Dow Jones News Service. An announcement made otherwise
    than to the London Stock Exchange or the Irish Stock Exchange shall be
    notified simultaneously to the London Stock Exchange and/or the Irish
    Stock Exchange as appropriate.
 
6. Rights of Withdrawal
 
(a) Except as otherwise provided in this paragraph 6, acceptances of the Offer
    in respect of Aran shares (including Aran shares represented by Aran ADSs)
    are irrevocable.
 
(b) Acceptances of the Offer may be withdrawn pursuant to the procedures set
    out below at any time prior to the Offer becoming unconditional (whether
    in accordance with its terms or by revision or waiver of its conditions),
    which in any event will not be prior to 3.00 p.m. (Dublin and London
    time), 10.00 a.m. (New York City time) on 23 September 1995. In the event
    of the Offer becoming unconditional, withdrawal rights will terminate
    immediately unless ARCO Irish Holdings fails to comply by 3.30 p.m.
    (Dublin and London time), 10.30 a.m. (New York City time) on the relevant
    day (or such later time(s) and date(s) as the Panel may agree) with the
    requirements specified in paragraph 5(a) (Announcements) in which case an
    accepting Aran securityholder may immediately withdraw his or her
    acceptance of the Offer in accordance with the provisions of this
    paragraph 6. This right of withdrawal may be terminated not less than
    eight days after the relevant day by ARCO Irish Holdings confirming, if
    such be the case, that the Offer is still unconditional, and complying
    with the other requirements specified in paragraph 5(a) (Announcements).
    If any such announcement is given, the first period of 14 days referred to
    in paragraph 1(c) (Acceptance period) will run from the date of such
    confirmation and compliance. For the purpose of this paragraph 6(b) the
    term "relevant day" has the meaning given to it in paragraph 5
    (Announcements).
 
(c) To be effective, a written notice of withdrawal (or, in respect of tenders
    made pursuant to a Letter of Transmittal only, a facsimile transmission
    thereof) must be timely received by the party (the Irish Receiving Agent,
    the UK Receiving Agent or the US Depositary) to whom the appropriate
    Acceptance Form was originally sent at one of the addresses set out on the
    back cover of this document and must specify the name of the person whose
    acceptance is to be withdrawn, the number of Aran ADSs and/or Aran shares
    to be withdrawn and (if an Aran share certificate or Aran ADR has been
    delivered) the name of the registered holder of the Aran securities, if
    different from the name of the person whose acceptance is to be withdrawn.
    In this paragraph 6, "written notice" (including any letter of
    appointment, direction or authority) means notice in writing bearing the
    original signature(s) of the relevant Aran securityholder or his or her
    agent duly appointed in writing (evidence of whose appointment in a form
    satisfactory to ARCO Irish Holdings is produced with the notice).
 
(d) In respect of Aran ADSs, if Aran ADRs have been delivered or otherwise
    identified to the US Depositary then, prior to the physical release of
    such Aran ADRs, the serial numbers shown on such Aran ADRs must be
    submitted and, unless the Aran ADSs evidenced by such Aran ADRs have been
    delivered by an Eligible Institution or the Offer accepted by means of a
    Letter of Transmittal, the signatures on the notice of withdrawal must be
    guaranteed by an Eligible Institution. If Aran ADSs have been delivered
    pursuant to the procedures for book-entry transfer set out in paragraph
    4(c) (Acceptance procedures for holders of Aran ADSs--Book-Entry Transfer
    Facilities) any notice of withdrawal must also specify the name and number
    of the account at the appropriate Book-Entry Transfer Facility to be
    credited with the withdrawn Aran ADSs and must otherwise comply with such
    Book-Entry Transfer Facility's procedures.
 
                                      28
<PAGE>
 
(e) All questions as to the validity (including time of receipt) of notices of
    withdrawal will be determined by ARCO Irish Holdings, whose determination
    (except as required by the Panel) shall be final and binding. None of ARCO
    Irish Holdings, Rothschilds, the Irish Receiving Agent, the UK Receiving
    Agent, the US Depositary, the US Dealer Manager, or any other person will
    be under any duty to give notification of any defects or irregularities in
    any notice of withdrawal or incur any liability for failure to give any
    such notification.
 
7. Revised Offer and Reduction of the Acceptance Condition
 
(a) Although no such revision is envisaged, if the Offer (in its original or
    any previously revised form) is revised and any such revision represents,
    on the date on which such revision is announced, (on such basis as
    Rothschilds may consider appropriate) an improvement (or no diminution) in
    the value of the consideration under the Offer as so revised compared with
    the value of the total consideration previously offered, the benefit of
    the revised Offer will, subject as provided in paragraphs 7(b) and (d) of
    this Part B, be deemed an acceptance of the Offer as revised and be made
    available to Aran securityholders who have accepted the Offer in its
    original or previously revised form(s) (hereinafter called "Previous
    Acceptors") and have not validly withdrawn their acceptance. The
    acceptance by or on behalf of a Previous Acceptor of the Offer in its
    original or any previously revised form(s) shall, subject as provided in
    paragraphs 7(b) and (c) of this Part B, constitute the separate
    appointment of ARCO Irish Holdings and/or any director of ARCO Irish
    Holdings and/or of Rothschilds as his attorney and/or agent with authority
    to accept any such revised Offer on behalf of such Previous Acceptor and,
    if such revised Offer includes alternative forms of consideration, to make
    elections and/or accept such alternative forms of consideration in such
    proportions as such attorney and/or agent in his absolute discretion
    thinks fit and to execute on behalf of and in the name of such Previous
    Acceptor all such further documents (if any) as may be required to give
    effect to such acceptances and/or elections. In making any such election,
    such attorney and agent shall take into account the nature of any previous
    acceptances and/or elections made by the Previous Acceptor and such other
    factors or matters as he may reasonably consider relevant.
 
(b) The authority referred to in paragraph 7(a) of this Part B and any
    acceptance of a revised Offer and any election pursuant thereto shall be
    irrevocable unless and until the Previous Acceptor has duly withdrawn his
    or her acceptance in accordance with paragraph 6 of this Part B (Rights of
    withdrawal).
 
(c) ARCO Irish Holdings reserves the right to treat an executed Acceptance
    Form relating to the Offer (in its original or any previously revised
    form(s)) which is received after the announcement or issue of the Offer in
    any revised form as a valid acceptance of the revised Offer and such
    acceptance shall constitute an authority in the terms of paragraph 7(a) of
    this Part B mutatis mutandis on behalf of the relevant Aran
    securityholder.
 
(d) The deemed acceptances and elections referred to in paragraph (a) of this
    paragraph 7 shall not apply and the power of attorney and authorities
    conferred by that paragraph shall be ineffective to the extent that a
    Previous Acceptor shall lodge, within 14 days of the posting of the
    document pursuant to which the revision of the Offer referred to in
    paragraph 7(a) is made available to Aran securityholders (or such later
    date as ARCO Irish Holdings may decide), a Form of Acceptance, Letter of
    Transmittal or some other form issued by or on behalf of ARCO Irish
    Holdings in which he or she validly elects (to the extent possible) to
    receive the consideration receivable by him or her under the revised Offer
    in some other manner.
 
(e) IN ACCORDANCE WITH A CONFIRMATION GIVEN IN CONNECTION WITH AN SEC
    EXEMPTIVE ORDER, ANY INTENTION TO REDUCE THE PERCENTAGE OF THE ARAN SHARES
    (INCLUDING ARAN SHARES REPRESENTED BY ARAN ADSs) TO WHICH THE OFFER
    RELATES IN RESPECT OF WHICH ARCO IRISH HOLDINGS MUST HAVE RECEIVED VALID
    ACCEPTANCES BEFORE THE ACCEPTANCE CONDITION CAN BE SATISFIED WILL BE
    ANNOUNCED BY ARCO IRISH HOLDINGS AT LEAST THREE US BUSINESS DAYS PRIOR TO
    THE DATE ON WHICH SUCH REDUCTION BECOMES EFFECTIVE. ARCO IRISH HOLDINGS
    WILL NOT, HOWEVER, NECESSARILY CAUSE THE OFFER TO REMAIN OPEN FOR ANY
    MINIMUM PERIOD AFTER SUCH REDUCTION OF THE ACCEPTANCE CONDITION HAS BECOME
    EFFECTIVE UNLESS THE OFFER BECOMES UNCONDITIONAL IN ALL RESPECTS IN WHICH
    EVENT IT WILL REMAIN OPEN FOR ACCEPTANCES FOR A FURTHER PERIOD OF NOT LESS
    THAN 14 DAYS.
 
8. General
 
(a) Save with the consent of the Panel, the Offer will lapse unless all the
    conditions have been fulfilled or (if capable of waiver) waived or, where
    appropriate, have been determined by ARCO Irish Holdings in its reasonable
    opinion to be or remain satisfied by midnight (Dublin and London time),
    8.00 p.m. (New York City time) on 24 October 1995 or such later date as
    ARCO Irish Holdings may, with the consent of the Panel, decide. ARCO Irish
    Holdings intends, if appropriate, to seek the Panel's approval to extend
    this date to not later than 14 November 1995, or such later date as the
    Panel may agree. If the Offer lapses for any reason, the Offer shall cease
    to be capable of further acceptance and ARCO Irish Holdings and Aran
    securityholders shall cease to be bound by prior acceptances.
 
                                      29
<PAGE>
 
(b) Except with the consent of the Panel, settlement of the consideration to
    which any Aran securityholder is entitled under the Offer will be
    implemented in full in accordance with the terms of the Offer without
    regard to any lien, right of set-off, counterclaim or other analogous
    right to which ARCO Irish Holdings may otherwise be, or claim to be,
    entitled as against such Aran securityholder and will (except with the
    consent of the Panel) be posted within 21 days of the later of the date on
    which the Offer becomes or is declared wholly unconditional and the date
    of receipt of a valid and complete Acceptance Form. Any cash consideration
    will be settled by way of cheque.
 
(c) Subject to paragraph 8(f) of this Part B, notwithstanding that no share
    certificate(s) and/or other document(s) of title is/are delivered in
    respect of it, a duly completed Form of Acceptance (i) executed under seal
    by SEPON Limited and endorsed on behalf of the Irish Stock Exchange or the
    London Stock Exchange to the effect that the Aran shares to which it
    refers are the whole or part of a holding registered in the name of SEPON
    Limited and/or are Aran shares to which SEPON Limited is unconditionally
    entitled immediately to become the registered holder, or (ii) executed by
    any other person(s) and endorsed on behalf of the Irish Stock Exchange or
    the London Stock Exchange to the effect that such person(s) is/are
    unconditionally entitled immediately to become the registered holder(s) of
    the Aran shares to which it refers and that one or more TALISMAN
    transfer(s) in favour of such person(s) in respect thereof is/are in the
    course of registration, shall be treated by ARCO Irish Holdings and
    Rothschilds as an acceptance valid and complete in all respects on the
    date of its actual receipt provided that, on its presentation to Aran's
    registrars, it is unconditionally accepted for registration.
 
(d) The terms, provisions, instructions and authorities contained in or deemed
    to be incorporated in the Acceptance Forms constitute part of the terms of
    the Offer.
 
(e) Notwithstanding the right reserved by ARCO Irish Holdings to treat a Form
    of Acceptance, a Letter of Transmittal or a Notice of Guaranteed Delivery
    as valid even though not entirely in order or (unless book-entry transfer
    of Aran ADSs has been made) not accompanied by the relevant share
    certificate(s), Aran ADRs and/or other documents of title and except as
    otherwise agreed with the Panel:
 
   (i)   an acceptance of the Offer will only be counted towards fulfilling
         the Acceptance Condition if the requirements of Note 4 and, if
         applicable, Note 6 on Rule 10 of the City Code are satisfied in
         respect of it;
 
   (ii)  a purchase of Aran shares or Aran ADSs by ARCO Irish Holdings or
         persons acting in concert with it or its nominee(s) will only be
         counted towards fulfilling the Acceptance Condition if the
         requirements of Note 5 and, if applicable, Note 6 on Rule 10 of the
         City Code are satisfied in respect of it; and
 
   (iii) the Offer will not become unconditional unless the UK Receiving
         Agent has issued a certificate to ARCO Irish Holdings or
         Rothschilds which states the number of Aran shares and Aran ADSs in
         respect of which acceptances have been received and not withdrawn
         which comply with paragraph 1(b) of this Part B and the number of
         Aran shares (including Aran shares represented by Aran ADSs)
         otherwise acquired, whether before or during the Offer period,
         which comply with the requirements of paragraph 1(b) of this Part
         B.
 
(f) The Offer and all acceptances of the Offer shall be governed by and
    construed in accordance with English law. Execution by or on behalf of a
    Aran securityholder of an Acceptance Form constitutes such
    securityholder's submission, in relation to all matters arising out of the
    Offer and the Acceptance Forms to the jurisdiction of the Courts of
    England; however, the conduct of the Offer is also subject to US federal
    securities laws and the securities laws of the states in the US in which
    the Offer is being made.
 
(g) All references in this document and in the Acceptance Forms to 23
    September 1995 shall (except in paragraph 8(b) of this Part B and where
    the context otherwise requires) be deemed, if the expiry date of the Offer
    be extended, to refer to the expiry date of the Offer as so extended.
 
(h) Any omission to despatch this document or any notice required to be
    despatched under the terms of the Offer to, or any failure to receive the
    same by, any person to whom the Offer is made, or should be made, shall
    not invalidate the Offer in any way.
 
(i) ARCO Irish Holdings and Rothschilds reserve the right to treat acceptances
    as valid if received by or on behalf of either of them at any place or
    places determined by them otherwise than as set out herein or in the
    Acceptance Forms.
 
                                      30
<PAGE>
 
(j) All powers of attorney, appointments of agents and authorities on the
    terms conferred by or referred to in this Appendix 1 or in the Acceptance
    Forms are given by way of security for the performance of the obligations
    of the Aran securityholder concerned and are irrevocable in accordance
    with section 4 of the UK Powers of Attorney Act 1971 except in the
    circumstances where the donor of such power of attorney or appointor is
    entitled to withdraw his acceptance in accordance with paragraph 6 of this
    Part B and duly does so.
 
(k) No acknowledgement of receipt of any Acceptance Forms, share
    certificate(s), Aran ADRs, and/or other document(s) of title will be
    given. All communications, notices, certificates, Aran ADRs, documents of
    title and remittances to be delivered by or sent to or from Aran
    securityholders (or their designated agent(s)) will be delivered by or
    sent to or from such Aran securityholders (or their designated agent(s))
    at their own risk.
 
(l) If the Offer lapses, the Acceptance Forms, share certificate(s), Aran ADRs
    and/or other document(s) of title will be returned by post (or by such
    other method as may be approved by the Panel) within 14 days of the Offer
    lapsing, at the risk of the person entitled thereto, to the person or
    agent whose name and address is set out in the relevant Box on the
    Acceptance Form or, if none is set out, to the first-named holder at
    his/her registered address outside Australia, Canada and Japan (or in the
    case of Aran ADSs delivered by book-entry transfer into the US
    Depositary's account at a Book-Entry Transfer Facility pursuant to the
    procedures set forth in paragraph 4(c) of this Part B (Acceptance
    procedures for holders of Aran ADSs--Book-Entry Transfer Facilities), such
    Aran ADSs will be credited within such period to an account maintained at
    the appropriate Book-Entry Transfer Facility).
 
(m) The Offer is made by this document and is capable of acceptance
    thereafter. Notification of the Offer appears in the Wall Street Journal
    on 25 August 1995 and will also appear in the International Herald
    Tribune. Acceptance Forms are available from the Irish Receiving Agent,
    the UK Receiving Agent and the US Depositary at the addresses set out on
    the back cover of this document from that time. Copies of this Offer
    document may be collected from the Irish Receiving Agent, the UK Receiving
    Agent, the US Depositary, and from Rothschilds, New Court, St Swithins
    Lane, London EC4P 4DU.
 
(n) If the Offer becomes or is declared unconditional in all respects and
    sufficient acceptances are received, ARCO Irish Holdings intends to apply
    the provisions of Section 204 of the Irish Companies Act to acquire
    compulsorily on the same terms as the Offer any outstanding Aran shares
    (including Aran shares represented by Aran ADSs) not acquired pursuant to
    the Offer or otherwise.
 
(o) The Aran shares (including Aran shares represented by Aran ADSs) will be
    acquired fully paid and free from all liens, equitable interests, charges
    and encumbrances and together with all rights attaching thereto, including
    voting rights and the right to receive all dividends and other
    distributions declared, made or paid after 21 August 1995.
 
9. Overseas Holders of Aran Shares and Aran ADSs
 
(a) The making of the Offer to persons not resident in Ireland, the United
    Kingdom or the US ("overseas holders") may be affected by the laws of the
    relevant jurisdiction. Such overseas holders should inform themselves
    about and observe any applicable legal requirements. It is the
    responsibility of any overseas holder wishing to accept the Offer to
    satisfy himself or herself as to the full observance of the laws of the
    relevant jurisdiction in connection therewith, including the obtaining of
    any governmental, exchange control or other consents which may be required
    or the compliance with other necessary formalities and the payment of any
    issue, transfer or other taxes due in such jurisdiction and ARCO Irish
    Holdings shall be entitled to be fully indemnified and held harmless by
    such overseas holder for any such issue, transfer or other taxes as ARCO
    Irish Holdings may be required to pay.
 
(b) The Offer is being made to all holders of Aran securities provided that
    receipt of this document does not constitute the making of the Offer to
    (and purported acceptance in respect of Aran securities will not be
    accepted from or on behalf of) Aran securityholders in any jurisdiction in
    the US or elsewhere in which the making of the Offer or the acceptance
    thereof would not be in compliance with the laws of such jurisdiction.
    ARCO Irish Holdings is not presently aware of any jurisdiction in the US
    that prohibits the making of the Offer.
 
(c) In those US jurisdictions whose securities laws or blue sky laws require
    the Offer to be made by a licensed broker or dealer, the Offer shall be
    deemed to be made on behalf of ARCO Irish Holdings by Rothschild Inc. or
    one or more registered brokers or dealers which are licensed under the
    laws of those jurisdictions.
 
(d) The provisions of this paragraph 9 supersede any terms of the Offer
    inconsistent herewith.
 
                                      31
<PAGE>
 
APPENDIX 2
 
Information Relating to ARCO and ARCO Irish Holdings
 
1. Directors and Executive Officers of ARCO
 
The following table sets forth the name, business address, present principal
occupation or employment, and material occupations, positions, offices or
employments for the past five years of each director and executive officer of
ARCO. All of the persons listed below are citizens of the United States. The
business address of each such person unless otherwise noted below is ARCO, 515
South Flower St., Los Angeles, CA 90071. In addition, except as otherwise
noted, each executive officer of ARCO has been employed by ARCO in the
positions listed below during the last five years.
 
<TABLE>
<CAPTION>
                                                  PRESENT PRINCIPAL OCCUPATION OR EMPLOYMENT
 NAME AND POSITION WITH ARCO                      POSITIONS AND FIVE-YEAR EMPLOYMENT HISTORY
 ---------------------------                      ------------------------------------------
 <C>                   <S>                        <C>
 Mike R. Bowlin,       Chairman of the Board,     Chairman of the Board since July 1995. Director
                       President, Chief           since 1992. Chief Executive Officer since July
                       Executive Officer and      1994, President and Chief Operating Officer since
                       Chief Operating Officer    June 1993, Executive Vice President (June 1992-
                                                  May 1993) and Senior Vice President (July 1985-
                                                  June 1992).

 Ronald J. Arnault,    Executive Vice President   Executive Vice President and Director since 1987.
                       and Chief Financial        Chief Financial Officer (June 1984-July 1990 and
                       Officer                    July 1992- present).

 Anthony G. Fernandes, Executive Vice President   Executive Vice President and Director since 1994.
                                                  Senior Vice President of ARCO and President of
                                                  ARCO Coal Company (July 1990-September 1994).

 William E. Wade, Jr., Executive Vice President   Executive Vice President and Director since 1993.
                                                  Senior Vice President of ARCO (May 1987-May
                                                  1993). President of ARCO Oil and Gas Company
                                                  (October 1990-May 1993).

 Lodwrick M. Cook,     Non-Executive Director     Retired from ARCO as Chairman of the Board
                                                  effective June 30, 1995. Director since 1980.
                                                  Chairman of the Board 1986-1995. Chief Executive
                                                  Officer (1985-1994).

 Frank D. Boren,       Non-Executive Director     Director since 1990. President of Sustainable
                                                  Conservation, San Francisco, CA, since June 1992.
                                                  President, The Nature Conservancy (1987-1990).

 Richard H. Deihl,     Non-Executive Director     Director since 1987. Former Chairman of the Board
                                                  (1986-1995), Chief Executive Officer (1983-1993),
                                                  and President (1983-1986) of H.F. Ahmanson &
                                                  Company (bank holding company).

 John Gavin,           Non-Executive Director     Director since 1989. Chairman of Gamma Services
                                                  International, Los Angeles, CA, (international
                                                  consulting services) since January 1990.

 Hanna H. Gray,        Non-Executive Director     Director since 1982. President Emeritus and Harry
                                                  Pratt Judson Distinguished Professor of History
                                                  of the University of Chicago, Chicago, IL, since
                                                  July 1993, President and Professor of History
                                                  (1978-1993).

 Philip M. Hawley,     Non-Executive Director     Director since 1975. Private consultant since his
                                                  retirement from Carter Hawley Hale Stores, Inc.
                                                  (department store) in April 1993. Chairman and
                                                  Chief Executive Officer (1983- 1993).

 Kent Kresa,           Non-Executive Director     Director since 1993. Chairman, President and
                                                  Chief Executive Officer of Northrop Grumman
                                                  Corporation, Los Angeles, CA, (aerospace) since
                                                  1990.
</TABLE>
 
                                      32
<PAGE>
 
<TABLE>
<CAPTION>
                                             PRESENT PRINCIPAL OCCUPATION OR EMPLOYMENT
NAME AND POSITION WITH ARCO                  POSITIONS AND FIVE-YEAR EMPLOYMENT HISTORY
---------------------------                  ------------------------------------------
<S>                   <C>                    <C>
David T. McLaughlin,  Non-Executive Director Director since 1993. Chairman since 1987, Chief
                                             Executive Officer since 1988 and President (1988-
                                             1994) of The Aspen Institute, Aspen, CO, (not-
                                             for-profit institute).

John B. Slaughter,    Non-Executive Director Director since 1989. President of Occidental
                                             College, Los Angeles, CA, since 1988.

Hicks B. Waldron,     Non-Executive Director Director since 1986. Former Chairman of the Board
                                             and Chief Executive Officer of Avon Products,
                                             Inc. (1984-1988).

Henry Wendt,          Non-Executive Director Director since 1987. Former Chairman of the Board
                                             SmithKline Beecham plc and its US subsidiary
                                             SmithKline Beecham Corporation (health care
                                             products) (1989-1994).
</TABLE>
 
2. Directors and Executive Officers of ARCO Irish Holdings
 
The following table sets forth the name, business address, present principal
occupation or employment, and material occupations, positions, offices or
employments for the past five years of each director and executive officer of
ARCO Irish Holdings. All of the persons listed below are citizens of the
United States. The business address of each such person is ARCO Irish Holdings
Inc., 515 South Flower St., Los Angeles, CA 90071. In addition, each executive
officer of ARCO Irish Holdings has been employed by ARCO in the positions with
ARCO listed below during the last five years.
 
<TABLE>
<CAPTION>
                                                  PRESENT POSITION WITH ARCO
 NAME AND POSITION WITH ARCO IRISH HOLDINGS       AND FIVE-YEAR EMPLOYMENT HISTORY
 ------------------------------------------       --------------------------------
 <C>                   <S>                        <C>
 William E. Wade, Jr., President and Chairman     See paragraph 1 above
                       of the Board

 Ronald J. Arnault,    Executive Vice President   See paragraph 1 above
                       and Director

 John B. Cheatham IV,  Senior Vice President      Senior Vice President, ARCO International Oil &
                       and Director               Gas Company since 1992, Senior Vice President,
                                                  ARCO Oil and Gas Company, (1991-1992), Vice
                                                  President, ARCO Oil and Gas Company (1989-1991).

 Terry G. Dallas,      Senior Vice President,     Vice President of ARCO since June 1993 and
                       Chief Financial Officer    Treasurer since January 1994. Vice-President
                       and Director               Corporate Planning (June 1993-January 1994) and
                                                  Assistant Treasurer, Corporate Finance of ARCO
                                                  (1990-1993).
</TABLE>
 
3. Principal Office
 
The principal office of ARCO and ARCO Irish Holdings is at 515 South Flower
St., Los Angeles, CA 90071. ARCO and ARCO Irish Holdings are incorporated in
the State of Delaware.
 
                                      33
<PAGE>
 
4. Financial Statements
 
The financial information for the three years ended 31 December 1994 relating
to ARCO contained in this section of the document has been extracted from the
published audited financial statements of ARCO for each of these years. The
financial information for the six months ended 30 June 1994 and 1995 has been
extracted from the unaudited published financial statements of ARCO for the
periods. ARCO's accounting policies conform to generally accepted accounting
principles in the United States including the "successful efforts" method of
accounting for oil and gas producing activities as set forth by the SEC.
Additional financial and other information for ARCO can be obtained from
ARCO's reports filed pursuant to the US Exchange Act. The information
contained herein is qualified in its entirety by reference to the complete
Reports on Form 10-K for the three years ended 31 December 1994 and on Forms
10-Q for the periods ended 31 March 1995 and 30 June 1995. ARCO's reports can
be inspected and copied at the public reference facilities maintained by the
SEC at Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549 and at the
following Regional Offices of the SEC: 7 World Trade Center, Suite 1300, New
York, NY 10048; and 500 West Madison Street, Suite 1400, Chicago, IL 60661.
Copies of such material can also be obtained by mail from the Public Reference
Section of the SEC at 450 Fifth Street, N.W., Washington, D.C. 20549, at
prescribed rates. In addition, such material may be inspected and copied at
the offices of the NYSE, 20 Broad Street, New York, New York 10005. Copies of
such material can also be obtained by writing to ARCO Investor Relations, 515
South Flower St., Los Angeles, CA 90071.
 
(a) CONSOLIDATED STATEMENTS OF INCOME OF ARCO FOR THE THREE YEARS ENDED 31
DECEMBER 1994
 
<TABLE>
<CAPTION>
US$ millions (except per share data)                       1992    1993    1994
<S>                                                      <C>     <C>     <C>
Total revenue                                            19,248  19,183  17,199
                                                         ------  ------  ------
Income before taxation, unusual items, gain on issuance
 of subsidiary stock and effect of changes in
 accounting policies                                      1,636   1,293   1,256
Unusual items                                               271    (659)   (347)
Gain on issuance of subsidiary stock                         --      --     459
                                                         ------  ------  ------
Income before taxation                                    1,907     634   1,368
Taxation                                                   (678)   (327)   (387)
                                                         ------  ------  ------
Income after taxation                                     1,229     307     981
Minority interests                                          (36)    (38)    (62)
                                                         ------  ------  ------
Income before cumulative effect of changes in
 accounting principles                                    1,193     269     919
Cumulative effect of changes in accounting principles      (392)     --      --
                                                         ------  ------  ------
Net income                                                  801     269     919
Cash dividends                                             (873)   (879)   (885)
                                                         ------  ------  ------
Retained (loss)/profit for the period                       (72)   (610)     34
                                                         ======  ======  ======
Earnings per share
Before cumulative effect of changes in accounting
 principles                                              $ 7.39  $ 1.66  $ 5.63
Cumulative effect of changes in accounting principles    $(2.43)     --      --
                                                         ------  ------  ------
Net income per share                                     $ 4.96  $ 1.66  $ 5.63
                                                         ======  ======  ======
Dividends per share                                      $ 5.50  $ 5.50  $ 5.50
                                                         ======  ======  ======
 
(b) RETAINED EARNINGS OF ARCO AT 31 DECEMBER 1992, 1993 AND 1994
 
<CAPTION>
US$ millions                                               1992    1993    1994
<S>                                                      <C>     <C>     <C>
Balance, 1 January                                        5,990   5,918   5,308
Net income                                                  801     269     919
Cash dividends
 Preference stocks                                           (3)     (3)     (3)
 Common stock                                              (870)   (876)   (882)
                                                         ------  ------  ------
Balance, 31 December                                      5,918   5,308   5,342
                                                         ======  ======  ======
</TABLE>
 
 
                                      34
<PAGE>
 
(c) ASSETS AND LIABILITIES OF ARCO AT 31 DECEMBER 1994
 
<TABLE>
<CAPTION>
                                                           US$ millions
<S>                                                        <C>
ASSETS
CURRENT ASSETS
 Cash and cash equivalents                                        1,394
 Short-term investments                                           2,991
 Other current assets                                             2,428
                                                                 ------
TOTAL CURRENT ASSETS                                              6,813

INVESTMENTS AND LONG-TERM RECEIVABLES                               645

FIXED ASSETS
 Property, plant and equipment                                   32,248
 Less accumulated depreciation, depletion and amortisation       16,526
                                                                 ------
                                                                 15,722
DEFERRED CHARGES AND OTHER ASSETS                                 1,383
                                                                 ------
TOTAL ASSETS                                                     24,563
                                                                 ======
LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES
 Notes payable                                                    1,478
 Accounts payable                                                   986
 Long-term debt due within one year                                 630
 Taxes payable, including excise tax                                253
 Other current liabilities                                        1,141
                                                                 ------
TOTAL CURRENT LIABILITIES                                         4,488

Long-term debt                                                    7,198
Deferred income taxes                                             2,721
Other deferred liabilities and credits                            3,471
Minority interest                                                   407

STOCKHOLDERS' EQUITY
 Preference stocks                                                    1
 Common stock                                                       402
 Capital in excess of par value of stock                            647
 Retained earnings                                                5,342
 Foreign currency translation                                       (51)
 Pension liability adjustment                                       (20)
 Treasury stock, at cost                                             (5)
 Net unrealised loss on investments                                 (38)
                                                                 ------
TOTAL STOCKHOLDERS' EQUITY                                        6,278
                                                                 ------
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY                       24,563
                                                                 ======
</TABLE>
 
(d) SUMMARISED CASH FLOWS OF ARCO FOR THE THREE YEARS ENDED 31 DECEMBER 1994
 
<TABLE>
<CAPTION>
US$ millions                                            1992    1993    1994
<S>                                                   <C>     <C>     <C>
Net cash provided by operating activities              3,079   2,762   2,097
Net cash used by investing activities                 (2,115) (2,237) (2,169)
Net cash used by financing activities                   (716)   (426)     (2)
Effect of exchange rate changes on cash                  (62)    (55)     10
                                                      ------  ------  ------
Net increase/(decrease) in cash and cash equivalents     186      44     (64)
Cash and cash equivalents at beginning of year         1,228   1,414   1,458
                                                      ------  ------  ------
Cash and cash equivalents at end of year               1,414   1,458   1,394
                                                      ======  ======  ======
</TABLE>
 
 
                                       35
<PAGE>
 
(e) SELECTED NOTES FROM THE PUBLISHED AUDITED FINANCIAL STATEMENTS OF ARCO
 
The following notes regarding significant accounting policies together with
other information in the notes to the financial statements which is of major
relevance to an appreciation of ARCO's financial information have been
extracted from the published financial statements of ARCO for the three years
ended 31 December 1994.
 
   (i) SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES OF ARCO
 
     Principles of consolidation
     The consolidated financial statements include the accounts of all
     subsidiaries, ventures and partnerships in which a controlling
     interest is held, including at 31 December 1994, ARCO Chemical Company
     of which ARCO owned 83.3% of the outstanding shares, and Vastar
     Resources, Inc. of which ARCO owned 82.3% of the outstanding shares.
     ARCO also consolidates its interests in undivided interest pipeline
     companies and in oil and gas and coal mining joint ventures. ARCO uses
     the equity method of accounting for companies where its ownership is
     between 20% and 50% and for other ventures and partnerships in which
     less than a controlling interest is held.
 
     Cash equivalents
     Cash equivalents consist of highly liquid investments, such as time
     deposits, certificates of deposit and marketable securities other than
     equity securities, maturing within three months of purchase. Cash
     equivalents are stated at cost, which approximates market value.
 
     Oil and gas unproved property costs
     Unproved property costs are capitalised and amortised on a composite
     basis, considering past success experience and average property life.
     In general, costs of properties surrendered or otherwise disposed of
     are charged to accumulated amortisation. Costs of successful
     properties are transferred to developed properties.
 
     Fixed assets
     Fixed assets are recorded at cost and are written off on either the
     unit-of-production or straight-line method based on the expected lives
     of individual assets or groups of assets.
 
     Upon disposal of assets depreciated on an individual basis, residual
     cost less salvage is included in current income. Upon disposal of
     assets depreciated on a group basis, unless unusual in nature or
     amount, residual cost less salvage is charged against accumulated
     depreciation.
 
     Dismantlement, restoration and reclamation costs
     The estimated costs, net of salvage value, of dismantling facilities
     or projects with limited lives or facilities that are required to be
     dismantled by contract, regulation or law, and the estimated costs of
     restoration and reclamation associated with oil and gas and mining
     operations are accrued during production and classified as a long-term
     liability. Such costs are taken into account in determining the cost
     of production in all operations, except oil and gas production, in
     which case such costs are considered in determining depreciation,
     depletion and amortisation.
 
     Environmental remediation
     Environmental remediation costs are accrued as operating expenses
     based on the estimated timing and extent of remedial actions required
     by applicable governmental authorities and the amount of ARCO's
     liability in consideration of the proportional liability and financial
     wherewithal of other responsible parties. Estimated liabilities are
     not discounted to present value.
 
     Reclassifications
     Certain previously reported amounts have been restated to conform to
     classifications adopted in 1994.
 
   (ii) UNUSUAL ITEMS
 
     During 1994, ARCO announced a restructuring program under which
     approximately 2,400 positions were eliminated. The program covered all
     operating units, excluding Lower 48 oil and gas operations, along
 
                                      36
<PAGE>
 
     with the corporate headquarters. ARCO provided as unusual items $347
     million before tax, consisting primarily of personnel costs (pension
     enhancements, severance and other ancillary costs) associated with the
     terminations.
 
     Approximately $155 million of the accrual related to severance and
     other ancillary costs which will be paid from ARCO's funds over the
     next two years. Approximately $110 million related to enhanced pension
     benefits which will be paid from the assets of qualified pension
     plans, not from ARCO funds. An additional $60 million is related to
     enhanced non-qualified pension benefits and postretirement benefits
     other than pensions which are currently unfunded. These benefits will
     be paid after retirement and over the remaining lives of the
     recipients; as such, it will not be practical to track the actual
     payments of these benefits.
 
     In 1993, ARCO announced a reorganisation of its Lower 48 oil and gas
     operations. ARCO provided as unusual items a pretax charge of $659
     million, of which $554 million related to the writedown for sale or
     other disposition of oil and gas properties and excess office space.
     In addition, amounts of $65 million, $35 million, and $5 million,
     respectively, were accrued for severance and ancillary costs, enhanced
     qualified pension benefits, and enhanced non-qualified pension
     benefits related to the elimination of approximately 1,300 positions.
 
     Through 31 December 1994, approximately 1,400 and 1,300 employees have
     been terminated under the 1994 and 1993 programs, respectively.
     Approximately $41 million and $47 million, respectively, of severance
     and ancillary benefits have been paid and charged against the 1994 and
     1993 accruals. Payments do not necessarily correlate with the number
     of terminations due to the ability of employees to defer receipt of
     certain payments.
 
     In 1992, ARCO recognised a pretax benefit of $149 million from the
     settlement with Iran related to ARCO's assets that had been
     nationalised in the late 1970s. ARCO also recognised a pretax benefit
     of $178 million related to a portion of the gain from the 1989 sale of
     a majority interest in Lyondell Petrochemical Company ("Lyondell")
     which was previously deferred as the amount equal to ARCO's guarantee
     of certain Lyondell notes. When Lyondell repaid the notes in 1992,
     ARCO was released from its guarantee and accordingly recognised the
     gain. ARCO also recognised a pretax charge of $56 million resulting
     from ARCO Chemical Company's withdrawal from the YUKONG ARCO Chemical
     Ltd. joint venture in Korea. The net benefit related to 1992 unusual
     items was $211 million after tax.
 
   (iii) GAIN ON ISSUANCE OF STOCK OF SUBSIDIARY
 
     In September 1993, ARCO established Vastar Resources, Inc., a wholly
     owned subsidiary of ARCO. Effective 1 October 1993, ARCO conveyed to
     Vastar beneficial title to certain producing properties together with
     certain developed and undeveloped acreage. Vastar is primarily engaged
     in the exploration for and the development and production of natural
     gas.
 
     In July 1994, ARCO recognised an after-tax gain of $273 million as a
     result of the initial public offering by Vastar of 17.7 per cent. of
     its common stock. ARCO owns the remaining 82.3 per cent. of the common
     stock of Vastar.
 
   (iv) ACCOUNTING CHANGES
 
     Effective 1 January 1992, ARCO adopted Statement of Financial
     Accounting Standards (SFAS) No. 106, "Employer's Accounting for
     Postretirement Benefits Other Than Pensions", SFAS No. 109,
     "Accounting for Income Taxes" and SFAS No. 112, "Employer's Accounting
     for Postemployment Benefits". The cumulative effect of adopting SFAS
     No. 106 resulted in a charge of $435 million, or $2.70 per share, to
     1992 earnings, net of income tax effects of approximately $262
     million. The cumulative effect of adopting SFAS No. 109 resulted in a
     benefit of $43 million, or $0.27 per share. There was no cumulative
     effect of adopting SFAS No. 112. Excluding the cumulative effects, the
     effect of adopting SFAS Nos. 106, 109 and 112 was not material to 1992
     net income.
 
                                      37
<PAGE>
 
   (v) EXTRACTS FROM THE NOTES TO THE PUBLISHED AUDITED FINANCIAL
       STATEMENTS OF ARCO FOR THE YEAR ENDED 31 DECEMBER 1994
 
     Fixed Assets
     Fixed assets at 31 December 1994 comprised:
 
<TABLE>
<CAPTION>
      US$ millions                                             1994
      <S>                                                   <C>
      Resources:
       Oil and gas                                           19,355
       Coal                                                   1,418
      Products:
       Refining and marketing                                 4,000
       Transportation                                         3,568
       Intermediate chemicals and specialty products          3,524
      Other                                                     383
                                                            -------
                                                             32,248
      Accumulated depreciation, depletion and amortization  (16,526)
                                                            -------
      Total                                                  15,722
                                                            =======
</TABLE>
 
     Segmental analysis
     ARCO operates primarily in Resources (upstream) and Products
     (downstream) segments. The Resources segment includes oil and gas
     operations, which comprise the exploration, development and production
     of petroleum, including petroleum liquids (crude oil, condensate and
     natural gas liquids) and natural gas; the purchase and sale of
     petroleum liquids and natural gas; and the mining and sale of coal.
     The Products segment includes the refining and transportation of
     petroleum and petroleum products; the marketing of petroleum products;
     and the manufacture and sale of intermediate chemicals and speciality
     products, including propylene oxide and derivatives, styrene monomer,
     tertiary butyl alcohol, and methyl tertiary butyl ether.
 
     Sales and other operating revenues by segment for the year ended 31
     December 1994 are as follows:
 
<TABLE>
<CAPTION>
      US$ millions                                   US  International  Total
      <S>                                          <C>     <C>           <C>
      Resources:
       Oil and gas                                  6,942      1,027      7,969
       Coal                                           327        336        663
      Products:
       Refining and marketing                       6,527          2      6,529
       Transportation                                 897         --        897
       Intermediate chemicals and specialty 
        products                                    2,213      1,210      3,423
      Other                                           --          30         30
      Elimination of intersegment amounts          (2,959)        --     (2,959)
                                                   ------      -----     ------
                                                   13,947      2,605     16,552
                                                   ======      =====     ------
      Income from equity investments, interest
       and other revenues                                                   647
                                                                         ------
                                                                         17,199
                                                                         ======
</TABLE>
 
     Long-term debt
     Maturities and sinking fund obligations for the five years subsequent
     to 31 December 1994 are as follows (millions of dollars): 1995--$630;
     1996--$1,234; 1997--$1,275; 1998--$177; 1999--$139.
 
 
     No material amounts of long-term debt are collateralized by ARCO
     assets.
 
     In 1994, ARCO and certain wholly owned subsidiaries had committed bank
     credit facilities of approximately $3.3 billion. At 31 December 1994,
     $115 million was borrowed under these committed facilities.
 
     Commitments and contingencies
     ARCO has commitments, including those related to the acquisition,
     construction and development of facilities, all made in the normal
     course of business.
 
                                      38
<PAGE>
 
     At 31 December 1994, there were contingent liabilities primarily with
     respect to guarantees of securities of other issuers of approximately
     $75 million.
 
     ARCO is subject to loss contingencies pursuant to federal, state and
     local environmental laws and regulations. These include possible
     obligations to remove or mitigate the effects on the environment of
     the disposal or release of certain chemical, mineral and petroleum
     substances at various sites, including the restoration of natural
     resources located at these sites and damages for loss of use and non-
     use values.
 
     The operations and consolidated financial position of ARCO continue to
     be affected from time to time in varying degrees by domestic and
     foreign political developments as well as legislation, regulations and
     litigation pertaining to restrictions on production, imports and
     exports, tax increases, environmental regulations, cancellation of
     contract rights and expropriation of property. Both the likelihood of
     such occurrences and their overall effect on ARCO vary greatly and are
     not predictable.
 
     These uncertainties are part of a number of items that ARCO has taken
     and will continue to take into account in periodically establishing
     reserves. Significant contingent liabilities are set out in the Annual
     Reports of ARCO.
 
     Retirement plans
     ARCO and its subsidiaries have defined benefit pension plans to
     provide pension benefits to substantially all employees. The benefits
     are based on years of service and the employee's compensation,
     primarily during the last three years of service. ARCO's funding
     policy is to make annual contributions as required by applicable
     regulations. ARCO accrues pension costs based on an actuarial
     valuation for each plan and funds the plans through contributions to
     trust funds that are kept apart from Company funds.
 
     Other postretirement benefits
     ARCO and its subsidiaries sponsor defined postretirement benefit plans
     to provide other postretirement benefits to substantially all
     employees who retire with ARCO having rendered the required years of
     service, along with their spouses and eligible dependents. Health care
     benefits are provided primarily through comprehensive indemnity plans.
     Currently, ARCO pays approximately 80% of the cost of such plans, but
     has the right to modify the cost-sharing provisions at any time. Life
     insurance benefits are based primarily on the employee's final
     compensation and are also partially paid for by retiree contributions,
     which vary based upon coverage chosen by the retiree.
 
     ARCO's current policy is to fund the cost of postretirement health
     care and life insurance plans on a pay-as-you-go basis.
 
     Earnings per share
     Earnings per share is based on the average number of common shares
     outstanding during each period including common stock equivalents that
     consist of certain outstanding options and all outstanding convertible
     securities. The average shares used in the calculation of earnings per
     share for the years ended 31 December 1992, 1993 and 1994 were 161.5
     million, 162.4 million and 163.2 million, respectively.
 
   (f) UNAUDITED FINANCIAL INFORMATION FOR THE SIX MONTHS, ENDED 30 JUNE
   1994 AND 1995
 
     (i) CONSOLIDATED PROFIT AND LOSS ACCOUNT FOR THE SIX MONTHS ENDED 30
     JUNE 1994 AND 1995
 
<TABLE>
<CAPTION>
      US$ millions (except per share data)    1994   1995
      <S>                                    <C>    <C>
      Total revenue                          8,262  9,142
                                             -----  -----
      Income before taxation                   275  1,183
      Taxation                                 (80)  (412)
                                             -----  -----
      Income after taxation                    195    771
      Minority interest                        (22)   (58)
                                             -----  -----
                                               173    713
                                             -----  -----
      Dividends                               (442)  (443)
                                             -----  -----
      Retained (loss)/profit for the period   (269)   270
                                             =====  =====
      Earnings per share                     $1.06  $4.36
                                             =====  =====
</TABLE>
 
                                      39
<PAGE>
 
   (ii) ASSETS AND LIABILITIES AT 30 JUNE 1995
 
<TABLE>
<CAPTION>
                                                                  US$ millions
      <S>                                                         <C>
      ASSETS
      CURRENT ASSETS:
       Cash and cash equivalents                                      1,288
       Short-term investments                                         2,254
       Other current assets                                           2,721
                                                                     ------
      TOTAL CURRENT ASSETS                                            6,263

      INVESTMENTS AND LONG-TERM RECEIVABLES                             778

      FIXED ASSETS:
       Property, plant and equipment                                 32,346
       Less accumulated depreciation, depletion and amortization     16,699
                                                                     ------
                                                                     15,647
      DEFERRED CHARGES AND OTHER ASSETS                               1,472
                                                                     ------
      TOTAL ASSETS                                                   24,160
                                                                     ======
      LIABILITIES AND STOCKHOLDERS' EQUITY
      CURRENT LIABILITIES:
       Notes payable                                                  1,203
       Accounts payable                                                 973
       Long-term debt due within one year                               684
       Taxes payable, including excise taxes                            285
       Other current liabilities                                      1,093
                                                                     ------
      TOTAL CURRENT LIABILITIES                                       4,238

      Long-term debt                                                  6,752
      Deferred income taxes                                           2,687
      Other deferred liabilities and credits                          3,420
      Minority interest                                                 453

      STOCKHOLDERS EQUITY:
       Preference stocks                                                  1
       Common stock                                                     402
       Capital in excess of par value of stock                          640
       Retained earnings                                              5,612
       Pension liability adjustment                                     (20)
       Net unrealized loss on investment                                (11)
       Foreign currency translation                                      (7)
       Treasury stock, at cost                                           (7)
                                                                     ------
      TOTAL STOCKHOLDERS' EQUITY                                      6,610
                                                                     ------
      TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY                     24,160
                                                                     ======
</TABLE>
 
5. Material Changes
 
Save as disclosed in this document, which includes summary information derived
from ARCO's unaudited published financial statements for the period ended 30
June 1995, there has been no material change in the financial or trading
position of ARCO since 31 December 1994, the date to which the latest
published audited financial statements were drawn up.
 
                                      40
<PAGE>
 
APPENDIX 3
 
Information Relating to Aran
 
1. Directors of Aran
 
The Directors of Aran are:
 
<TABLE>
<S>                   <C>
Michael J. Whelan     Chairman, Chief Executive Officer and Managing Director
Paul M. Creedon       Finance Director
Thomas C. Earls       Exploration and Production Director
Peter D. Gorman       Director of Corporate Planning and Secretary
Alastair J. Woodrow   Managing Director of Aran Energy Exploration Ltd. and Director
Rodney B. Dockrell    Non-Executive Director
Lord Ezra of Horsham  Non-Executive Director
Desmond A. Hanafin    Non-Executive Director
Howard E. Kilroy      Non-Executive Director
Thomas J. Maher       Non-Executive Director
</TABLE>
 
2. Principal and Registered Office
 
The principal and registered office of Aran is at Elm House, Clanwilliam
Court, Lower Mount Street, Dublin 2, Ireland. Aran is registered in Ireland
under number 039227.
 
3. Additional Background on Aran
 
This information and data is derived from Aran's 1994 Annual Report and its
Report on Form 20-F filed with the SEC for the year ended 31 December 1994.
 
Aran explores for, develops and produces oil and gas. Aran's principal
activities are in UK sector of the North Sea, the US Gulf Coast area and
offshore Ireland.
 
Aran is incorporated in Ireland. Aran's shares are listed on the Irish Stock
Exchange and the London Stock Exchange, and its ADSs are quoted on NASDAQ.
 
Aran's primary producing assets include an approximate 14 per cent. working
interest in the Dunlin field, an approximate 5 per cent. working interest in
the Alba Field and an approximate 15 per cent. working interest in the Gryphon
field in the UK as well as interests in the South Pass 37 and East Potash
fields in the US. Aran also has royalty interests in production from the
Kinsale Head and Ballycotton gas fields operated offshore Ireland. Commercial
reserves stand at 56 million barrels of oil equivalent with US proved SEC
reserves of 42 million barrels of oil equivalent. Approximately 83 per cent.
of Aran's reserves are located in the UK with 15 per cent. in the US and 2 per
cent. in Ireland. Total net production in 1994 was 15.1 thousand barrels
equivalent per day.
 
Aran's exploration and appraisal drilling efforts are carried out in the UK
North Sea, US Gulf Coast, offshore Ireland and Turkey. A recent exploration
success, the Schiehallion discovery, lies in the West of Shetlands area of the
UK North Sea. Appraisal work is currently being carried out to assess the size
of the extension of the Schiehallion field into the acreage in which Aran has
an interest.
 
In Ireland, Aran holds a 100 per cent. interest in and is the operator of the
Connemara oilfield, located off the west coast of Ireland. Aran participated
in the discovery well, which was drilled in 1979, but as at 31 December 1994
Aran had not established a commercial development.
 
Aran is also engaged in the importation and sale of oil products in Ireland
through its 85 per cent. owned subsidiary, Estuary Fuel Ltd. Fuel oil, gas
oil, petrol and other products are marketed in the south, south-west and west
of Ireland. The minority interest in Estuary is owned by agricultural
cooperatives.
 
                                      41
<PAGE>
 
4. Financial Statements
 
The financial information contained in this section of the document has been
extracted from the audited consolidated financial statements of Aran for the
three years ended 31 December 1994 without adjustment. The information set out
below does not constitute statutory accounts within the meaning of the Irish
Companies Act. Full accounts which have been prepared in accordance with
accounting standards currently applicable in Ireland have been delivered to
the Registrar of Companies in Ireland for each of the three years up to and
including the year ended 31 December 1994. Unqualified audit reports in
accordance with the requirements of the Irish Companies Act have been given by
Arthur Andersen, Andersen House, International Financial Services Centre,
Dublin 1, Republic of Ireland for the three years ended 31 December 1994,
being the auditors of Aran for the relevant financial periods. Additional
financial and other information for the Aran Group can be obtained from Aran's
reports under the US Exchange Act, which can be inspected and copied at the
public reference facilities maintained by the SEC at Room 1024, 450 Fifth
Street, N.W., Washington, D.C. 20549 and at the following Regional Offices of
the SEC: 7 World Trade Center, Suite 1300, New York, NY 10048; and 500 West
Madison Street, Suite 1400, Chicago, IL 60661. Copies of such material can
also be obtained by mail from the Public Reference Section of the SEC at 450
Fifth Street, N.W., Washington, D.C. 20549, at prescribed rates.
 
(a) CONSOLIDATED PROFIT AND LOSS ACCOUNTS OF ARAN FOR THE THREE YEARS ENDED 31
DECEMBER 1994
 
<TABLE>
<CAPTION>
IR(Pounds)000 (except per share data)            1992     1993     1994
<S>                                           <C>      <C>      <C>
Turnover                                       45,054   63,911   83,449
Cost of sales                                 (39,583) (54,961) (71,232)
Exceptional items                                  --       --    3,403
                                              -------  -------  -------
Gross Profit                                    5,471    8,950   15,620
Distribution and administrative expenses       (2,317)  (2,871)  (4,053)
                                              -------  -------  -------
Operating Profit                                3,154    6,079   11,567
Interest receivable and similar income            581      842      580
Interest payable and similar charges             (702)  (1,226)  (5,247)
                                              -------  -------  -------
Profit on ordinary activities before tax        3,033    5,695    6,900
Tax on profit on ordinary activities               --   (1,317)  (1,426)
Tax effect of exceptional items                    --       --   (1,799)
                                              -------  -------  -------
Profit on ordinary activities after taxation    3,033    4,378    3,675
Minority interests                                 --       (8)     (19)
                                              -------  -------  -------
Profit for the financial year                   3,033    4,370    3,656
Balance, beginning of year                    (34,690) (31,657)  13,251
Set off against share premium account              --   40,538       --
                                              -------  -------  -------
Balance, end of year                          (31,657)  13,251   16,907
                                              =======  =======  =======
Earnings per share                              1.16p    1.67p    1.40p
                                              =======  =======  =======
Dividends per share                                0p       0p       0p
                                              =======  =======  =======
 
(b) RECONCILIATION OF MOVEMENTS IN SHAREHOLDERS' FUNDS AT 31 DECEMBER 1992,
1993 AND 1994
 
<CAPTION>
IR(Pounds)000                                    1992     1993     1994
<S>                                           <C>      <C>      <C>
Profit for the financial year                   3,033    4,370    3,656
Currency translation differences                 (634)   7,427   (3,539)
New share capital subscribed                       --      113        4
                                              -------  -------  -------
Net addition to shareholders' funds             2,399   11,910      121
Opening shareholders' funds                    65,539   67,938   79,848
                                              -------  -------  -------
Closing shareholders' funds                    67,938   79,848   79,969
                                              =======  =======  =======
</TABLE>
 
                                      42
<PAGE>
 
(c) ASSETS AND LIABILITIES OF ARAN AT 31 DECEMBER 1994
 
<TABLE>
<CAPTION>
                                                         IR(Pounds)000
<S>                                                      <C>
FIXED ASSETS
 Oil and gas interests                                      159,631
 Other tangible assets                                        2,679
                                                            -------
                                                            162,310
CURRENT ASSETS
 Stocks                                                       2,419
 Debtors                                                     12,407
 Cash at bank and in hand                                     6,792
                                                            -------
                                                             21,618
 Creditors: amounts falling due within one year             (24,873)
                                                            -------
 Net current liabilities                                     (3,255)
                                                            -------
 Total assets less current liabilities                      159,055
 Creditors: amounts falling due after more than one year    (67,302)
 Provisions for liabilities and charges                     (11,746)
 Minority Interests                                             (38)
                                                            -------
NET ASSETS                                                   79,969
                                                            =======
CAPITAL AND RESERVES
 Called up share capital                                     52,318
 Share premium account                                       11,935
 Foreign currency translation reserve                        (1,191)
 Profit and loss account                                     16,907
                                                            -------
SHAREHOLDERS' FUNDS                                          79,969
                                                            =======
</TABLE>
 
(d) SUMMARISED CASH FLOWS FOR THE THREE YEARS ENDED 31 DECEMBER 1994
 
<TABLE>
<CAPTION>
IR(Pounds)000                                        1992     1993     1994
<S>                                               <C>      <C>      <C>
Net cash inflow from operating activities           9,010   19,202   24,609
Net cash outflow from returns on investments and
 servicing of finance                                (992)  (1,350)  (4,358)
Tax (paid)/refunded                                  (592)  (4,980)   1,349
Net cash outflow from investing activities        (37,041) (61,537) (31,640)
                                                  -------  -------  -------
Net cash outflow before financing                 (29,615) (48,665) (10,040)
                                                  =======  =======  =======
Net cash inflow from financing                    (27,026) (52,649)  (3,893)
(Decrease)/increase in cash and cash equivalents   (2,589)   3,984   (6,147)
                                                  -------  -------  -------
                                                  (29,615) (48,665) (10,040)
                                                  =======  =======  =======
</TABLE>
 
(e) SELECTED NOTES FROM THE PUBLISHED AUDITED ACCOUNTS OF ARAN
 
The following notes regarding significant accounting policies together with
other information in the notes to the accounts which may be of relevance to an
appreciation of Aran's financial information have been extracted from the
published accounts of Aran for the three years ended 31 December 1994.
 
   (i) SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
     The financial statements have been prepared under the historical cost
     convention. The principal accounting policies adopted by the Group are
     as follows:
 
     Principles of consolidation
     The consolidated financial statements include the financial statements
     of Aran and all of its subsidiaries; all intercompany transactions and
     balances have been eliminated in their preparation.
 
                                      43
<PAGE>
 
     Acquisitions are dealt with on the purchase basis of accounting
     whereby the assets acquired are recorded at their fair value with any
     difference being taken to goodwill or capital reserve as appropriate.
     Goodwill is written off directly against reserves immediately on
     acquisition. The results of subsidiaries acquired or disposed of in
     the period are included in the consolidated profit and loss account
     from the date of acquisition or up to the date of disposal.
 
     Turnover
     Turnover principally comprises revenues from oil and gas producing
     properties, from the sale of oil products (inclusive of Excise Duties
     and exclusive of Value Added Tax), and from overriding royalties.
 
     Pension costs
     The Group provides pensions to substantially all employees through a
     variety of contributions to a variety of separately administered
     schemes, including both defined contribution and defined benefit
     schemes.
 
     The amounts charged to the profit and loss account in respect of
     defined benefit schemes is the estimated regular cost of providing the
     benefits accrued in the period (as advised by professionally qualified
     actuaries), adjusted to reflect variations from that cost. The regular
     cost is calculated so that it represents a substantially level
     percentage of current and future pensionable payroll. Variations from
     regular cost are charged or credited to the profit and loss account
     over the average remaining service lives of employees. The amount
     charged to the profit and loss account in relation to defined
     contribution schemes is the amount payable in respect of the year.
 
     Any difference between amounts charged to the profit and loss account
     and contributions paid to pension schemes is included in "Debtors" or
     "Creditors" in the balance sheet.
 
     Taxation
 
     (i) Corporation Tax
     Corporation Tax is provided on taxable profits at current rates.
 
     The taxation liabilities of certain Group companies are reduced wholly
     or in part by the surrender of losses by fellow Group companies.
 
     Deferred tax (which arises from differences in the timing of the
     recognition of items, principally depreciation, in the financial
     statements and by the tax authorities) has been calculated on the
     liability method. Deferred tax is provided on timing differences which
     will probably reverse, at the rates of tax likely to be in force at
     the time of reversal. Deferred tax is not provided on timing
     differences which will probably not reverse.
 
     (ii) Petroleum Revenue Tax
     Petroleum Revenue Tax is provided on a unit of production basis over
     the expected life of the field after taking account of uplift, oil
     allowance, safeguard and abandonment costs, using relevant oil prices
     and costs at the balance sheet date. Allowable exploration and
     appraisal expenditures and cross field allowances are taken against
     the unit of production charge in the year in which they become
     allowable; excess amounts are carried forward in the unit of
     production calculation of the field most likely to take the benefit of
     the expenditure.
 
     Oil and gas interests
 
     (i) Exploration, appraisal and development expenditure
     The Group accounts for oil and gas expenditure under the "full cost"
     method of accounting.
 
     Exploration, appraisal and development expenditure is incurred either
     through consortium operations or directly on acquiring, exploring or
     testing exploration prospects. All lease and license acquisition
     costs, geological and geophysical costs and other direct costs of
     exploration, appraisal and development are capitalised. The amount
     capitalised includes general and administrative costs directly related
     to these activities, interest expense incurred on loans prior to the
     commencement of production and costs incurred in reviewing potential
     acquisitions of exploration/production interests. Investment income
     (net of related taxes), arising on funds held for exploration,
     appraisal or development, is credited against these costs in so far as
     it exceeds interest payable.
 
                                      44
<PAGE>
 
     (ii) Cost pools
     Costs are capitalised within three separate geographical cost pools:
     United Kingdom and other areas, United States of America and Ireland.
 
     Costs relating to the exploration and appraisal of oil and gas
     interests which the Directors consider to be unevaluated are initially
     held outside the cost pools. Costs held outside cost pools are
     reassessed at each year end. When these interests are considered to be
     commercially producible, or there is evidence of impairment, the
     related costs are transferred to the relevant cost pools.
 
     Proceeds from the disposal of part or all of an interest which is held
     outside a cost pool are credited to that interest with any excess
     being credited to the relevant cost pools.
 
     (iii) Ceiling tests
     A ceiling test is carried out at each balance sheet date to assess
     whether the net book value of the capitalised costs in each pool,
     together with the future costs of development of undeveloped reserves,
     is covered by the undiscounted future net revenues from the reserves
     within that pool, calculated at year-end prices. Any deficiency
     arising is provided for to the extent that, in the opinion of the
     Directors, it is considered to represent a permanent diminution in the
     value of the related asset, and, where provided, is dealt with in the
     profit and loss account as additional depreciation.
 
     (iv) Depreciation
     Expenditure within each cost pool is depreciated using the ratio of
     the production in the period to the estimated quantity of commercial
     reserves at the end of the period plus the production in the period.
     Costs used in the unit of production calculation comprise the net book
     value of capitalised costs plus the anticipated future costs of
     development of the undeveloped reserves at current period end
     unescalated prices. Changes in cost and reserve estimates are dealt
     with prospectively.
 
     Other tangible fixed assets
     Other tangible fixed assets are stated at cost net of depreciation.
     Depreciation is provided at the following annual rates, on a straight
     line basis, to write off the cost in these assets over their estimated
     useful lives:
 
<TABLE>
<CAPTION>
        Leasehold buildings    Term of lease
        <S>                    <C>
        Plant and machinery      12.5-33%
        Fixtures and fittings      10-33%
        Motor vehicles             15-25%
</TABLE>
 
     Depreciation is not provided on freehold land.
 
     Stocks
     Stocks, with the exception of under and over liftings of crude oil,
     principally comprise oil and oil products, and are stated at the lower
     of first-in, first-out cost and net realisable value. Cost includes
     all expenditure incurred in bringing each product to its present
     location and condition. Net realisable value is based on estimated
     normal selling price less further costs expected to be incurred on
     disposal. Provision is made for obsolete, slow moving or defective
     items where appropriate. Under and over liftings of crude oil are
     stated at market value at the balance sheet date.
 
     Leases
     Where assets are financed by leasing agreements that give rights
     approximating to ownership ("finance leases") they are recorded as
     tangible fixed assets and the corresponding liability is included in
     "Creditors". Depreciation on such leased assets is charged to the
     profit and loss account on the same basis as for other tangible fixed
     assets. The interest portion of payments made under such lease
     agreements is also charged to the profit and loss account so as to
     produce a constant periodic rate of charge. All other leases are
     "operating leases" and the lease rentals are charged to the profit and
     loss account in the period in which they are incurred.
 
     Abandonment
     Provision is made for the removal of facilities and site restoration
     at the end of the producing life of a field on a unit of production
     basis using the operator's current estimate of costs. Changes in
     estimated costs are accounted for prospectively.
 
 
                                      45
<PAGE>
 
     Foreign currency
     In the financial statements of individual companies, transactions
     denominated in foreign currencies are recorded in the local currency
     at actual exchange rates as of the date of the transaction. Monetary
     assets and liabilities denominated in foreign currencies at period end
     are translated at the rates of exchange prevailing at that date. Any
     gain or loss arising in a trading subsidiary from a change in exchange
     rates subsequent to the date of the transaction is included as an
     exchange gain or loss in the profit and loss account.
 
     For the purposes of consolidation the closing rate/net investment
     method is used, under which translation gains and losses are shown as
     a movement on the foreign currency translation reserve. Profit and
     loss accounts and cash flows of overseas subsidiaries are translated
     at average exchange rates.
 
     Certain US dollar denominated assets and related US dollar borrowings
     are treated as a group of assets and liabilities and are accounted for
     in foreign currency. Foreign exchange differences arising on the
     retranslation of these US dollar borrowings, to the extent that they
     relate to investment in oil and gas fields which generate US dollar
     income, are taken to foreign currency translation reserve, together
     with the exchange differences arising on the retranslation of the US
     dollar denominated assets.
 
     Treasury instruments
     From time to time the Group enters into transactions in the normal
     course of business using a variety of treasury instruments in order to
     hedge against exposures to exchange rate variations and interest rate
     fluctuations. These transactions are accounted for in accordance with
     their economic substance.
 
   (ii) EXTRACTS FROM NOTES TO THE PUBLISHED AUDITED ACCOUNTS OF ARAN FOR
        THE YEAR ENDED 31 DECEMBER 1994
 
     Exceptional items
 
<TABLE>
<CAPTION>
      IR(Pounds)000                                          1994
      <S>                                                  <C>
      Write back of abandonment provision on disposal (a)   1,385
      Write back of over provision for abandonment (b)      2,018
                                                           ------
                                                            3,403
      Tax effect of exceptional items (c)                  (1,799)
                                                           ------
      Net effect of exceptional items                       1,604
                                                           ======
</TABLE>
 
     (a) On disposal of its interest in the Forties oilfield during the
         year, the Group was released from any liability for cost to be
         incurred on the future abandonment of that field; consequently,
         the provision charged in prior years for Forties abandonment costs
         was written back.
 
     (b) As a result of a revision to the estimated cost of abandonment of
         the Dunlin oilfield, part of the abandonment provision set up on
         acquisition of the Group's interest in that oilfield in July 1992
         has been released.
 
     (c) As a result of the exceptional items above, the charges for
         Deferred Petroleum Revenue Tax and Deferred Corporation Tax have
         been increased by IR(Pounds)1,009,000 and IR(Pounds)790,000,
         respectively.
 
     Segmental reporting
 
     (a) By class of business
<TABLE>
<CAPTION>
                                     Oil and gas
                                      production Oil distribution Group total
      IR(Pounds)000                         1994             1994        1994
      <S>                            <C>         <C>              <C>
      Sales to third parties              56,893           26,556      83,449
                                         =======           ======     =======
      Operating profit after
       exceptional items                  11,383              184      11,567
                                         =======           ======
      Net interest expense                                             (4,667)
                                                                      -------
      Group profit before taxation                                      6,900
                                                                      =======
      Net assets                         150,260            3,921     154,181
                                         =======           ======
      Bank loans and overdrafts net
       of cash                                                        (74,212)
                                                                      -------
      Group net assets                                                 79,969
                                                                      =======
</TABLE>
 
 
                                      46
<PAGE>
 
     (b) By geographical area by origin
<TABLE>
<CAPTION>
                                                          UK and
                                     Ireland     US  other areas Group total
      IR(Pounds)000                     1994   1994         1994        1994
      <S>                            <C>     <C>     <C>         <C>
      Sales to third parties          27,656  6,814       48,979      83,449
                                      ====== ======      =======     =======
      Operating profit after
       exceptional items                 622    (51)      10,996      11,567
                                      ====== ======      =======
      Net interest expense                                            (4,667)
                                                                     -------
      Group profit before taxation                                     6,900
                                                                     =======
      Net assets                       9,017 21,829      123,335     154,181
                                      ====== ======      =======
      Bank loans and overdrafts net
       of cash                                                       (74,212)
                                                                     -------
      Group net assets                                                79,969
                                                                     =======
</TABLE>
 
     Analysis of sales to third parties by geographical destination is not
     materially different from the analysis of sales by origin.
 
     Tax on profit on ordinary activities
 
<TABLE>
<CAPTION>
      IR(Pounds)000                           1994
      <S>                                    <C>
      Ireland
      Corporation Tax at 40%
        --charge for year                       --
        --refund of tax paid in prior years    (57)
      Deferred Corporation Tax                 (62)
                                             -----
                                              (119)
                                             -----
      United Kingdom
      Deferred Corporation Tax               1,512
      Deferred Petroleum Revenue Tax            33
      Tax effect of exceptional items        1,799
                                             -----
                                             3,344
                                             -----
                                             3,225
                                             =====
</TABLE>
 
     Earnings per ordinary share
     The calculation of earnings per ordinary share is based on the profit
     for the financial year of IR(Pounds)3,656,000 (1993--
     IR(Pounds)4,370,000: 1992--IR(Pounds)3,033,000) and on 261,575,062
     ordinary shares (1993--261,359,859: 1992--261,063,240), being the
     average number of shares in issue for the year.
 
     Analysis of borrowings
 
<TABLE>
<CAPTION>
      IR(Pounds)000                                                    1994
      <S>                                                           <C>
      Bank loans and overdrafts are repayable as follows:
        --in less than one year                                      13,702
        --in between one and two years                               18,837
        --in between two and five years                              37,476
        --in five years or more                                      10,989
                                                                    -------
      Total borrowings                                               81,004
      Included in "Creditors: amounts falling due within one year"  (13,702)
                                                                    -------
      Included in "Creditors: amounts falling due after more than
       one year"                                                     67,302
                                                                    =======
</TABLE>
 
     Bank loans of $112.5 million were drawn under the Group's 10 year
     borrowing base facility which can provide funds up to a maximum of
     $197.5 million. The amount available and the timing of repayments is
     determined by reference to the valuation of assets included in the
     borrowing base and is recomputed bi-annually. The facility is secured
     by a floating charge on the assets of Aran Energy Exploration Limited
     and Aran Energy Corporation and by a fixed charge on the shares in
     these subsidiaries.
 
                                      47
<PAGE>
 
     $10.6 million was outstanding on five year loan notes issued in March
     1994 by a US subsidiary, Aran Energy USA Inc., to finance the
     acquisition and initial redevelopment of the East Potash oil and gas
     field in Louisiana, USA. These notes are secured by fixed charges on
     the East Potash field and on the shares in that subsidiary.
 
     Bank loans and overdrafts include an amount of IR(Pounds)1.5 million
     drawn down by Estuary Fuel Limited under short term facilities.
     Borrowings under these facilities are secured by a first fixed and
     floating charge over the assets of that subsidiary.
 
     Pension arrangements
     The Group operates a number of pension schemes for employees. All
     schemes are externally funded; some are defined contribution, while
     others are defined benefit. The pension charge for the year was
     IR(Pounds)256,000.
 
     Contributions to the defined benefit scheme are assessed in accordance
     with the advice of a qualified actuary using the attained age method.
     The most recent actuarial reviews were carried out in January 1993. At
     that date the market value of the assets of the defined benefit
     schemes was IR(Pounds)376,000 which was sufficient to cover the
     benefits that had accrued to members after allowing for expected
     future increases in salaries. The main actuarial assumption was that
     the return on scheme investments would exceed salary increases by 2%
     per annum. Reports of the actuaries are not available for public
     inspection.
 
5. Material Changes
 
The members of the bid committee of ARCO and the Directors of ARCO Irish
Holdings are not aware of any material changes in the financial or trading
position of Aran since 31 December 1994, the date to which the latest
published audited consolidated accounts of Aran were drawn up.
 
 
                                      48
<PAGE>
 
APPENDIX 4
 
Additional Information Relevant to the Offer
 
1. Responsibility for Information in this Document
 
The directors of ARCO Irish Holdings, whose names are set out in paragraph 2
of Appendix 2 of this document, and the members of the bid committee of ARCO,
whose names are set out below, accept responsibility for the information
contained in this document, save that the only responsibility accepted by them
in respect of the information contained in this document relating to the Aran
Group, which has been compiled from publicly available sources, has been to
ensure that such information has been correctly compiled and is correctly and
fairly reproduced and presented. Save as aforesaid, to the best of the
knowledge and belief of the directors of ARCO Irish Holdings and the bid
committee of ARCO (who have taken all reasonable care to ensure that such is
the case), the information contained in this document is in accordance with
the facts and does not omit anything likely to affect the import of such
information.
 
2. Responsible Persons
 
(a) The directors of ARCO Irish Holdings are set out in paragraph 2 of Appendix
2 of this document.
 
(b) The members of the bid committee of ARCO are as follows:
 
     Mike R. Bowlin
     Ronald J. Arnault
     Anthony G. Fernandes
     William E. Wade
 
3. ARCO's Reasons for the Offer and Plans for Aran
 
The purpose of the Offer is to enable ARCO Irish Holdings to acquire all of
Aran's equity securities. ARCO Irish Holdings currently intends, as soon as
practicable after consummation of the Offer, to seek maximum representation on
Aran's board of directors and, if permitted, to acquire on the same terms as
the Offer pursuant to the compulsory acquisition procedures of Section 204 of
the Irish Companies Act any Aran shares (including any Aran shares represented
by Aran ADSs) not purchased pursuant to the Offer or otherwise held by ARCO
Irish Holdings (and any person acting in concert with ARCO Irish Holdings).
Further information is contained in paragraph 9 (Compulsory acquisition).
 
It is anticipated that ARCO and ARCO Irish Holdings will, from time to time
after completion of the Offer, evaluate and review Aran's assets, corporate
structure, capitalisation, operations, properties, policies, management and
personnel and consider what, if any, changes would be desirable in light of
the circumstances which then exist. Such changes could include (i) a sale of
assets or interests therein, (ii) the transfer of assets between members of
the Aran Group and members of the ARCO Group or (iii) changes in Aran's
business, corporate structure, Memorandum and Articles of Association,
capitalisation, dividend policy and management. Neither ARCO nor ARCO Irish
Holdings has any present plans or proposals with respect to any of such
matters except as otherwise disclosed in this document.
 
Save as disclosed in this document, none of ARCO or ARCO Irish Holdings or, to
the best of their knowledge, any of their respective executive officers,
directors or subsidiaries has had any business relationship or transactions
with Aran or any of its executive officers, directors or affiliates that would
require reporting under the rules and regulations of the SEC.
 
4. Background to the Offer
 
Except as hereinafter set forth, since 1 January 1992, there have been no
contacts, negotiations, or transactions between ARCO, ARCO Irish Holdings, any
of their respective directors, executive officers or subsidiaries and Aran or
its affiliates concerning a public offer or other acquisition of securities; a
merger, consolidation or acquisition; an election of directors; or a sale or
other transfer of a material amount of assets. On 19 August 1995, ARCO advised
Morgan Grenfell & Co. Limited, in their capacity as financial advisers to
Aran, that it intended to announce the Offer on 21 August 1995.
 
5. Amount and Source of Funds
 
The amount required to pay the cash consideration for the Aran shares
(including Aran shares represented by Aran ADSs and subject to issuance
pursuant to option scheme(s)), together with estimated fees and expenses, is
estimated to be IR(Pounds)164 million.
 
                                      49
<PAGE>
 
The Offer will be financed out of existing cash resources available to the
ARCO Group. Neither the payment of interest on, nor repayment of, nor security
for, any liability (contingent or otherwise) of the ARCO Group will depend to
any significant extent on the business of the Aran Group.
 
Rothschilds is satisfied that the necessary resources are available to ARCO
Irish Holdings to enable it to implement the Offer in full.
 
6. ARCO Irish Holdings
 
ARCO Irish Holdings was incorporated on 2 August 1995 in Delaware, US for the
purpose of making the Offer. ARCO Irish Holdings is an indirect, wholly owned
subsidiary of ARCO. The principal office of ARCO Irish Holdings is at 515
South Flower St., Los Angeles, CA 90071.
 
The directors of ARCO Irish Holdings are as set out in paragraph 2 of Appendix
2 of this document.
 
7. Disclosure of Interests and Dealings in Aran Shares
 
In this paragraph 7, "disclosure period" means the period commenced on 21
August 1994 (the date 12 months prior to the commencement of the Offer period
as defined in the City Code) and ended on 23 August 1995 (the latest
practicable date prior to the posting of this document).
 
(a) As at 23 August 1995 (the latest practicable date prior to the posting of
    this document), there were no Aran shares (including Aran shares
    represented by Aran ADSs) or shares convertible into, rights to subscribe
    for or options (including traded options) in respect of such shares
    ("Relevant Securities"), held or controlled by, or (in the case of the
    directors and their families) the subject of an interest, direct or
    indirect, held by any of the following:
 
   (i)   ARCO and ARCO Irish Holdings;
 
   (ii)  the directors and the executive officers of each of ARCO and ARCO
         Irish Holdings, their close relatives or related trusts;
 
   (iii) the associates (within the meaning of the US Exchange Act) and
         majority-owned subsidiaries of ARCO, ARCO Irish Holdings, their
         directors and their executive officers;
 
   (iv)  an associate (as hereinafter defined) of ARCO or ARCO Irish
         Holdings;
 
   (v)   any person with whom ARCO or ARCO Irish Holdings or any of their
         respective associates (as hereinafter defined) has any arrangement of
         the kind referred to in paragraph (b) below; or
 
   (vi)  any other person acting in concert with ARCO or ARCO Irish Holdings,
 
   and no dealings for value by any of these parties have been made in
   respect of any Relevant Securities during the disclosure period.
 
(b) Save as disclosed in this document, there are no arrangements (including
    indemnity or option arrangements), agreements or understandings, formal or
    informal, of whatever nature to which ARCO or ARCO Irish Holdings or any
    of their respective associates (as hereinafter defined) is a party
    relating to Relevant Securities which may be an inducement to deal or
    refrain from dealing.
 
(c) None of ARCO or ARCO Irish Holdings or, to the best of their knowledge,
    any of the persons listed in paragraph 1 or paragraph 2 of Appendix 2, any
    associate (within the meaning of the US Exchange Act) or majority owned
    subsidiary of ARCO, ARCO Irish Holdings or any of the persons so listed,
    or any of the respective directors, executive officers or subsidiaries of
    any of the foregoing has effected any transaction in any Aran security
    during the past 60 days.
 
(d) There are no contracts, arrangements, understandings or relationships
    between ARCO, ARCO Irish Holdings or any of their respective executive
    officers or directors and any person with respect to Aran securities
    (including, but not limited to, any contract, arrangement, understanding
    or relationship concerning the transfer or the voting of any of such
    securities, joint ventures, loan or option arrangements, puts or calls,
    guarantees of loans, guarantees against loss, or the giving or withholding
    of proxies, consents or authorisations).
 
References in this Appendix 4 to:
 
(1) an "associate" (unless otherwise provided herein) are to:
 
   (i) subsidiaries and associated companies (as to which see paragraph
       (iii) below) of ARCO or ARCO Irish Holdings and companies of which
       any such subsidiaries or associated companies are associated
       companies;
 
                                      50
<PAGE>
 
   (ii)  banks, financial and other professional advisers (including
         stockbrokers but excluding exempt market makers and exempt fund
         managers) to ARCO or ARCO Irish Holdings, or a company referred to
         in (i) above, including persons controlling, controlled by or under
         the same control as, such banks or financial or other professional
         advisers;
 
   (iii) the directors of ARCO or ARCO Irish Holdings and the directors of
         any company referred to in (i) above (together in each case with
         any member of their immediate families or related trusts); and
 
   (iv)  the pension funds of ARCO or ARCO Irish Holdings or a company
         referred to in (i) above:
 
(2) a "bank" do not apply to a bank whose sole relationship with ARCO or ARCO
    Irish Holdings or a company referred to in (a)(i) above is the provision
    of normal commercial banking services or such activities in connection
    with the Offer as handling acceptances and other registration work; and
 
(3) ownership or control of 20 per cent. or more of the equity share capital
    of a company are regarded as the test of associated company status and
    "control" means a holding, or aggregate holdings, of shares carrying 30
    per cent. or more of the voting rights attributable to the share capital
    of the company which are currently exercisable at a general meeting,
    irrespective of whether the holding gives de facto control.
 
8. Market Price Data and Principal Purchases
 
Aran shares are listed and traded on the Irish Stock Exchange and the London
Stock Exchange and Aran ADSs on NASDAQ. The following table sets out, for the
periods indicated (i) the reported closing highest and lowest share prices for
Aran shares on the Irish Stock Exchange as derived from the Irish Stock
Exchange Daily Official List, (ii) the reported closing highest and lowest
middle market quotations for Aran shares on the London Stock Exchange as
derived from the Daily Official List of the London Stock Exchange and (iii)
the high and low ADS prices, on NASDAQ as reported by Datastream. For current
price information, Aran securityholders are urged to consult publicly
available sources.
 
<TABLE>
<CAPTION>
                       Irish Stock Exchange    London Stock Exchange         NASDAQ
                                Aran shares              Aran shares     Aran ADSs*
                                 (IR pence)              (Stg pence)          (US$)
                            High        Low         High        Low     High   Low
<S>                   <C>        <C>           <C>        <C>           <C>   <C>
Calendar 1993
 Third Quarter              40.0       27.0         36.5       24.5      n/a   n/a
 Fourth Quarter             36.0       21.3         33.5       21.5      n/a   n/a
Calendar 1994
 First Quarter              30.5       25.5         29.5       24.5      n/a   n/a
 Second Quarter             35.0       25.0         33.5       24.5      n/a   n/a
 Third Quarter              41.0       30.0         39.5       30.5    17.50 16.25
 Fourth Quarter             44.5       36.8         43.5       36.5    21.13 17.25
Calendar 1995
 First Quarter              47.0       43.0         46.5       42.5    22.88 20.06
 Second Quarter             46.0       36.8         46.0       39.5    22.50 19.38
 Third Quarter (up to
  and including 18
  August)                   43.5       36.8         44.3       39.5    21.25 18.75
</TABLE>
-------
* Aran ADSs were quoted on NASDAQ from 20 September 1994.
 
The following table shows the middle market quotations for Aran shares as
derived from the London Stock Exchange Daily Official List and last dealt
prices as derived from the Irish Stock Exchange Daily Official List and the
Aran ADS price on NASDAQ as reported by Datastream for (i) the first business
day of each month from February to August 1995; (ii) 18 August 1995 (the last
business day prior to the announcement of the Offer); and (iii) 23 August 1995
(the latest practicable date prior to the posting of this document):
 
<TABLE>
<CAPTION>
                      Irish Stock Exchange    London Stock Exchange       NASDAQ
                               Aran shares              Aran shares    Aran ADSs
                                (IR pence)              (Stg pence)        (US$)
<S>                   <C>                     <C>                      <C>
1 February 1995                       43.5                     43.0        20.40
1 March 1995                          47.0                     46.5        22.00
3 April 1995                          46.0                     46.0        22.50
1 May 1995 (2 May in
 Ireland)                             44.0                     44.5        21.75
1 June 1995                           41.0                     42.0        20.50
3 July 1995                           36.8                     39.5        19.44
1 August 1995                         41.0                     42.5        20.69
18 August 1995                        42.5                     44.3        20.63
23 August 1995                        65.3                     67.3        32.25
</TABLE>
 
 
                                      51
<PAGE>
 
In accordance with normal UK practice, ARCO Irish Holdings or its nominees or
brokers (acting as agents for ARCO Irish Holdings) or a subsidiary of ARCO
(other than ARCO Irish Holdings) or a special purpose company established and
jointly owned by ARCO and Rothschilds, may make certain purchases of Aran
securities during the period in which the Offer remains open for acceptance
pursuant to relief granted from the SEC staff from Rule 10b-13 under the US
Exchange Act. In accordance with the terms of this relief, among other things,
(i) such purchases may not be effected within the United States, (ii)
information regarding such purchases must be disclosed in the United States by
press release to the extent disclosure is required pursuant to the City Code,
and (iii) ARCO Irish Holdings and Rothschilds and any such other persons must
comply with any applicable rules of UK and Irish organisations.
 
9. Compulsory Acquisition
 
If, as a result of the Offer and subject to certain conditions, ARCO Irish
Holdings receives acceptances of the Offer in respect of Aran shares
(including Aran shares represented by Aran ADSs) representing at least 80 per
cent. in value of the Aran shares (including Aran shares represented by Aran
ADSs) to which the Offer relates, then provided such requirement is achieved
within four months of 25 August 1995, ARCO Irish Holdings will be entitled and
intends to effect the compulsory acquisition procedures provided for in
Section 204 of the Irish Companies Act to compel the purchase of any
outstanding Aran shares (including Aran shares represented by Aran ADSs) on
the terms of the Offer in accordance with the relevant procedures and time
limits described in Section 204 of such Act. If, as a result of the Offer and
otherwise and subject to certain conditions, ARCO Irish Holdings acquires or
is deemed to acquire a beneficial interest in Aran shares (including Aran
shares represented by Aran ADSs) representing 80 per cent. in value of issued
Aran shares (including Aran shares represented by Aran ADSs) a holder of Aran
shares (including Aran shares represented by Aran ADSs) may require ARCO Irish
Holdings to purchase his or her Aran shares (including Aran shares represented
by Aran ADSs) on the terms of the Offer in accordance with the relevant
procedures and time limits described in Section 204 of such Act.
 
If for any reason the above mentioned compulsory acquisition procedures are
not invoked, ARCO Irish Holdings will evaluate other alternatives to obtain
the remaining Aran shares (including those represented by Aran ADSs) not
purchased pursuant to the Offer or otherwise. Such alternatives could include
acquiring additional Aran shares or Aran ADSs in the open market, in privately
negotiated transactions, in another offer to purchase, by means of a scheme of
arrangement under the Irish Companies Act, or otherwise. Any such additional
acquisitions could be for a consideration greater or less than, or equal to,
the consideration for Aran shares and Aran ADSs in the Offer. However, under
the City Code, except with the consent of the Panel, ARCO Irish Holdings may
not acquire any Aran shares or Aran ADSs on better terms than those of the
Offer within six months of the termination of the Offer if ARCO Irish
Holdings, together with any persons acting in concert with it (as defined by
the City Code), holds shares carrying more than 50 per cent. of the voting
rights normally exercisable at general meetings of Aran.
 
Holders of Aran shares (including Aran shares represented by Aran ADSs) do not
have appraisal rights as a result of the Offer. However, in the event that the
compulsory acquisition procedures referred to above are available to ARCO
Irish Holdings, holders of Aran shares (including Aran shares represented by
Aran ADSs) whose Aran shares (including those represented by Aran ADSs) have
not been purchased pursuant to the Offer will have certain rights to object
under Section 204 of the Irish Companies Act .
 
Section 204 of the Irish Companies Act is reproduced in Appendix 5.
 
10. Certain Consequences of the Offer
 
(a) Market effect
 
The purchase of Aran securities pursuant to the Offer will reduce the number
of Aran securityholders and the number of the Aran shares and Aran ADSs that
might otherwise trade publicly and, depending upon the number of Aran
securities so purchased, could adversely affect the liquidity and market value
of the remaining Aran shares and Aran ADSs held by the public. In addition,
Aran shares will cease to be listed on the Irish Stock Exchange and the London
Stock Exchange and quoted on NASDAQ if ARCO Irish Holdings completes the
compulsory acquisition procedures referred to in paragraph 9 above.
 
If the Aran ADSs were to cease to be traded on NASDAQ, it is possible that
they would continue to trade in the over-the-counter market and that price
quotations would be reported. The extent of the public market for the Aran
ADSs and the availability of such quotations would, however, depend upon such
factors as the number of holders remaining
 
                                      52
<PAGE>
 
at such time, the interest on the part of securities firms in maintaining a
market in Aran ADSs, the possible termination of registration under the US
Exchange Act as described below, the termination of listing of the Aran shares
on the Irish Stock Exchange and the London Stock Exchange and other factors.
 
(b) Public availability of information
 
In the event that Aran shares continue to be listed on the Irish Stock
Exchange or London Stock Exchange following the purchase of Aran securities
pursuant to the Offer, Aran securityholders who have not tendered their Aran
securities pursuant to the Offer will continue to receive the same financial
and other information from Aran that Aran presently is required by the rules
of the Irish Stock Exchange and the London Stock Exchange to send to such Aran
securityholders. If Aran shares are no longer listed on the Irish Stock
Exchange and the London Stock Exchange following the Offer, Aran would no
longer be required by those rules to make publicly available such financial
and other information but Aran would be required by the Irish Companies Act to
send its audited annual accounts to Aran securityholders.
 
Aran shares represented by Aran ADSs currently are registered under the US
Exchange Act. Registration of such Aran shares evidenced by the Aran ADSs may
be terminated upon application of Aran to the SEC if Aran ADSs are neither
listed on a national securities exchange nor held by 300 or more holders of
record in the US. Termination of registration of the Aran shares evidenced by
Aran ADRs under the US Exchange Act would substantially reduce the information
required to be furnished by Aran to holders of Aran ADSs and to the SEC and
would make certain provisions of the US Exchange Act, such as the requirements
of Rule 13e-3 thereunder with respect to "going private" transactions, no
longer applicable to Aran. Further, "affiliates" of Aran and persons "holding
restricted" securities of Aran may be deprived of the ability to dispose of
such securities pursuant to Rule 144 promulgated under the US Securities Act.
If, as a result of the purchase of the Aran ADSs evidenced by Aran ADRs
pursuant to the Offer and prior to completing the compulsory acquisition
procedures referred to in paragraph 9 above, Aran is not required to maintain
registration of the Aran shares evidenced by the Aran ADSs under the US
Exchange Act, ARCO Irish Holdings intends to cause Aran to apply for
termination of such registration. If registration of the Aran shares evidenced
by Aran ADSs is not terminated prior to completion of the aforementioned
compulsory acquisition procedures, then Aran ADSs will cease trading on NASDAQ
and the registration of the Aran shares represented by Aran ADSs under the US
Exchange Act would be terminated following completion of the aforementioned
compulsory acquisition procedures.
 
(c) Margin Securities
 
Aran ADSs currently are "margin securities" under the regulations of the Board
of Governors of the US Federal Reserve System, which status has the effect,
among other things, of allowing US brokers to extend credit on the collateral
of Aran ADSs for purposes of buying, carrying and trading in securities
("Purpose Loans"). Depending on factors such as the number of holders of
record of Aran ADSs and the number and market value of publicly held Aran ADSs
following the purchase of Aran shares (including Aran shares represented by
Aran ADSs) pursuant to the Offer, ARCO Irish Holdings intends to request the
termination of the trading of Aran ADSs on NASDAQ. As a result, Aran ADSs
might no longer constitute margin securities and, therefore, could no longer
be used as collateral for Purpose Loans made by US brokers. In addition, if
registration of the Aran shares evidenced by Aran ADSs under the US Exchange
Act were terminated, Aran ADSs would no longer constitute "margin securities".
 
11. Legal and Regulatory Matters
 
(a) General
 
Except as set out herein and other than in compliance with the Panel's
requirements in relation to the City Code and with the US securities laws,
ARCO Irish Holdings is not aware of (i) any licence or regulatory permit that
appears to be material to the business of Aran and its subsidiaries, taken as
a whole, which might be adversely affected by ARCO Irish Holdings' acquisition
of Aran securities as contemplated herein or (ii) any approval or other action
by any domestic or foreign governmental, administrative or regulatory agency
or authority that appears to be material to Aran and its subsidiaries, taken
as a whole, and required for the acquisition or ownership of Aran securities
by ARCO Irish Holdings as contemplated herein. Should any such approval or
other action be required, ARCO Irish Holdings currently contemplates that such
approval or other action would be sought. There can be no assurance that any
such approval or other action, if needed, would be obtained without
substantial conditions attached thereto or that failure to obtain any such
approval or other action might not result in consequences adverse to Aran's
business.
 
(b) UK competition laws
 
ARCO Irish Holdings is seeking confirmation in terms satisfactory to it from
the UK Office of Fair Trading that it is not the intention of the UK Secretary
of State for Trade and Industry to refer the proposed acquisition of Aran by
 
                                      53
<PAGE>
 
ARCO Irish Holdings to the UK Monopolies and Mergers Commission. The Offer
will lapse if the proposed acquisition of Aran by ARCO Irish Holdings is
referred to the UK Monopolies and Mergers Commission before 3.00 p.m. (Dublin
and London time), 10.00 a.m. (New York City time) on 23 September 1995 or the
date on which the Offer becomes unconditional in all respects, whichever is
the later.
 
(c) US antitrust laws
 
The Offer is subject to the US HSR Act, which provides that certain
acquisition transactions may not be consummated until certain information has
been furnished to the Antitrust Division of the Department of Justice (the
"Antitrust Division") and the Federal Trade Commission (the "FTC"). Pursuant
to the US HSR Act, ARCO has filed a Notification and Report Form relating to
the Offer with the Antitrust Division and the FTC, and one of such US agencies
will have responsibility for reviewing the Form. The waiting period under the
US HSR Act applicable to the Offer will expire 15 calendar days after the date
of filing, unless early termination of the waiting period is granted or ARCO
receives a request for additional information or documentary material from the
Antitrust Division or FTC prior thereto. If the Antitrust Division or FTC were
to request additional information or documentary material from ARCO the
waiting period would expire ten calendar days after the date of substantial
compliance with such request. Thereafter, the waiting period could be extended
only by court order or with the consent of ARCO. The additional ten calendar
day waiting period may be terminated sooner by the Antitrust Division or FTC.
 
The FTC and the Antitrust Division frequently scrutinise the legality under
the US antitrust laws of transactions such as the proposed acquisition of the
Aran securities by ARCO Irish Holdings pursuant to the Offer. At any time
before or after the purchase of the Aran securities, the FTC or the Antitrust
Division could take such action under the US antitrust laws as it deems
necessary or desirable in the public interest, including seeking to enjoin the
purchase of the Aran securities pursuant to the Offer, or seeking divestiture
of the Aran securities purchased by ARCO Irish Holdings or the divestiture of
substantial assets of ARCO, its affiliates or Aran. Private parties may also
bring legal action under the US antitrust laws in certain circumstances. Based
upon an examination of publicly available information relating to the
businesses in which the ARCO Group and the Aran Group are engaged, ARCO and
ARCO Irish Holdings believe that the Offer does not violate the US antitrust
laws. Nevertheless, there can be no assurance that a challenge to the Offer on
US antitrust grounds will not be made or, if such a challenge is made, of the
result.
 
(d) Irish competition laws
 
The Offer will be notified to the Minister for Enterprise and Employment of
Ireland pursuant to Section 5 of the Mergers Act. The Offer is conditional
upon the Minister for Enterprise and Employment of Ireland having stated in
writing that he does not intend to make an order under Section 9 of the
Mergers Act in relation to the Offer or, in the event of the said Minister
making an order subject to conditions, ARCO Irish Holdings in its absolute
discretion having decided to accept such conditions or, in the event of no
such order being made and the said Minister not stating in writing that he
does not intend to make such an order, the relevant period within the meaning
of Section 6 of the Mergers Act having expired.
 
(e) US environmental matters
 
Under various US state environmental laws, the transfer of ownership of a
facility may require notification to the state or other parties or a clean-up
of any environmental contamination. In addition, under US state and federal
environmental laws, permits used for the operation of facilities may require
new financial guarantees upon the occurrence of a change of ownership of Aran.
ARCO Irish Holdings does not anticipate that any environmental requirements
will delay completion of the Offer.
 
(f) US state takeover laws
 
A number of states of the US have adopted takeover laws and regulations which
purport, in varying degrees, to be applicable to attempts to acquire
securities of corporations which have substantial assets, securityholders,
principal executive offices or principal places of business in such states.
ARCO Irish Holdings believes that no such US state takeover statutes apply to
the Offer and ARCO Irish Holdings has not attempted to comply with any such US
state takeover statutes in connection with the Offer. ARCO Irish Holdings
reserves the right to challenge the validity or applicability of any US state
law allegedly applicable to the Offer and nothing in this document nor any
action taken in connection herewith is intended as a waiver of that right. In
the event that any US state takeover statute is asserted to be applicable to
the Offer and an appropriate court does not determine that such law or
regulation is not applicable to the Offer, ARCO Irish Holdings might be
required to file certain information with, or to receive approvals from, the
relevant US state authorities and might be unable to purchase Aran securities
pursuant to the Offer or be delayed in
 
                                      54
<PAGE>
 
continuing or consummating the Offer. In such case, ARCO Irish Holdings may
not be obligated to purchase such Aran securities.
 
(g) Laws of other jurisdictions
 
Aran and certain of its subsidiaries conduct business in certain countries in
addition to Ireland, the UK and the US where regulatory filings or approvals
may be required in connection with the Offer. Certain of such filings or
approvals, if required, may not be made or obtained prior to the expiration of
the Offer. There is no assurance that any such approvals would be obtained or
that adverse consequences to ARCO's or Aran's business might not result from a
failure to obtain such approvals or from conditions that might be imposed in
connection therewith.
 
12. United States Federal Income Taxation
 
This summary addresses certain United States federal income tax consequences
applicable to holders of Aran securities who are citizens or residents of the
United States, domestic corporations or otherwise taxed as United States
residents. This summary is based on the Internal Revenue Code of 1986, as
amended (the "Code"), administrative pronouncements, judicial decisions and
existing and proposed Treasury Regulations, changes to any of which (possibly
retroactive) may affect the tax consequences described herein. This summary
assumes that the Aran securities have been held as capital assets. This
summary also assumes that Aran is not and has never been a passive foreign
investment company for US federal income tax purposes. This summary does not
discuss all tax consequences that may be relevant to a holder of Aran
securities in light of such holder's particular circumstances or to holders
subject to special rules, such as certain financial institutions, regulated
investment companies, insurance companies, dealers in securities, exempt
organisations and holders who are residents of countries other than the United
States or whose functional currency is not the United States dollar.
 
In general, a holder of Aran securities who sells such securities pursuant to
the Offer will, for United States federal income tax purposes, recognise a
gain or loss equal to the difference between such holder's adjusted tax basis
in the Aran securities transferred and the amount of cash received in exchange
therefor. Such gain or loss will generally be capital gain or loss and will be
long-term capital gain or loss if, on the date of sale, the Aran securities
were held for more than one year. A holder of Aran securities who sells such
securities pursuant to the Offer may have a foreign currency exchange gain or
loss for United States federal income tax purposes which would be treated as
ordinary income or loss. Any such exchange gain or loss would be in addition
to the gain or loss realised by the holder on the disposition of Aran
securities pursuant to the Offer.
 
If Aran is or was during a five-year look back period a controlled foreign
corporation (within the meaning of section 957 of the Code), any United States
person that directly, indirectly or constructively owns or owned 10 per cent.
or more of the combined voting power of all classes of its voting stock ("Ten
Percent US Shareholder") during any portion of such period when Aran was a
controlled foreign corporation may be subject to special rules under section
1248 of the Code. Ten Percent US Shareholders should consult their United
States tax advisers regarding the effect of any section 338 election that ARCO
may make with respect to Aran and its subsidiaries and the application of
section 1248 of the Code to their sale of Aran securities pursuant to the
Offer.
 
A holder of Aran securities may be subject to backup withholding with respect
to the cash payment if (i) the payee fails to furnish a taxpayer
identification number ("TIN") to the payer or establish an exemption from
backup withholding, (ii) the US Internal Revenue Service notifies the payer
the TIN furnished by the payee is incorrect, (iii) there has been a notified
payee underreporting with respect to interest or dividends described in
section 3406(c) of the Code or (iv) there is a failure of the payee to certify
under the penalty of perjury that the payee is not subject to withholding as
described in section 3406 of the Code.
 
To prevent US back-up federal income tax withholding on any cash payment
delivered pursuant to the Offer, each holder of Aran ADSs who accepts the
Offer by means of the Letter of Transmittal and each Aran shareholder who
accepts the Offer by sending the Form of Acceptance to the US Depositary must
provide the US depositary with his or her correct taxpayer identification
number and certify that he or she is not subject to US back-up federal income
tax withholding by completing the substitute Form W-9 included in the Letter
of Transmittal or Form of Acceptance, or, if the holder is a non-resident
alien or foreign entity for US federal income tax purposes, establish an
exemption from US back-up federal income tax withholding by completing the
substitute form W-8, Certificate of Foreign Status, a copy of which is
available, upon request, from either the US Depositary or the US Internal
Revenue Service.
 
The foregoing discussion is for general information only and is intended to be
a summary of the principal United States federal income tax considerations of
the Offer. Each holder of Aran securities should consult its own tax adviser
concerning the United States federal and applicable state, local, foreign and
other tax consequences to the Offer.
 
                                      55
<PAGE>
 
13. Fees and Expenses
 
Rothschilds is acting as financial adviser to ARCO and ARCO Irish Holdings in
connection with the Offer. Rothschilds will receive reasonable and customary
compensation for its services as financial adviser to ARCO and ARCO Irish
Holdings together with reimbursement for its reasonable out of pocket
expenses. Pursuant to a letter from ARCO dated 26 July 1995 and addressed to
Rothschilds, ARCO has agreed to indemnify Rothschilds and certain others
against, inter alia, certain losses and expenses arising out of the engagement
or performance by Rothschilds of its duties to advise and assist ARCO and ARCO
Irish Holdings in connection with the Offer including liabilities under the US
federal securities laws.
 
Pursuant to a letter dated 25 August 1995, ARCO and ARCO Irish Holdings have
retained Rothschild Inc., an affiliate of Rothschilds, as US Dealer Manager
for the Offer (the "US Dealer Manager Agreement") in the United States to
perform those services in connection with the Offer as are customarily
performed in the United States by investment banking concerns acting as
dealer-manager in connection with offers of a like nature and in respect of
which Rothschild Inc. will receive reimbursement including its out-of-pocket
expenses. Under the terms of the US Dealer Manager Agreement, ARCO has agreed
to indemnify Rothschild Inc. and certain other persons against certain
liabilities and expenses which may be incurred in connection with the Offer
including liabilities under the US federal securities laws.
 
Hoare Govett and Riada are stockbrokers to ARCO and ARCO Irish Holdings in
connection with the Offer, and will receive a reasonable and customary fee for
services in connection with the Offer. Pursuant to a letter from ARCO dated 31
July 1995 and addressed to Hoare Govett, ARCO has agreed to indemnify Hoare
Govett and certain others including Riada against, inter alia, certain losses
and expenses arising out of the engagement or performance by Hoare Govett and
Riada of their duties to advise and assist ARCO and ARCO Irish Holdings in
connection with the Offer.
 
ARCO Irish Holdings has retained AIB Bank as the Irish Receiving Agent, The
Royal Bank of Scotland plc as the UK Receiving Agent and First Chicago Trust
Company of New York as the US Depositary. ARCO Irish Holdings will pay the
Irish Receiving Agent, the UK Receiving Agent and the US Depositary reasonable
and customary compensation for their services in connection with the Offer,
together with reimbursement of out-of-pocket expenses. ARCO will indemnify the
US Depositary against certain liabilities and expenses in connection
therewith, including liabilities under the US federal securities laws.
Brokers, dealers, commercial banks and trust companies will be reimbursed by
ARCO for customary mailing and handling expenses incurred by them in
forwarding material to their customers.
 
ARCO and ARCO Irish Holdings will not pay any fees or commissions to any
broker or dealer or any other person for soliciting acceptances of the Offer
(other than Rothschilds, Rothschild Inc., Hoare Govett or Riada as described
above).
 
14. Bases of Calculation and Sources of Information
 
(a) The value of the issued capital of Aran at the Offer price is based on
    261,591,729 Aran shares (including Aran shares represented by Aran ADSs)
    in issue, as disclosed in the Extel card for Aran dated 23 August 1995.
 
(b) The share price high in Dublin of Aran for the last four years is derived
    from the Irish Stock Exchange Daily Official List.
 
(c) Applicable exchange rates as derived from the Financial Times dated 24
    August 1995:
 
    IR(Pounds)1 = Stg(Pounds)1.022
 
    IR(Pounds)1 = $1.5771
 
(d) The graph shown on the inside cover of this document is derived from the
    share prices as reported by Datastream for each Friday in the four years
    from the week commencing 19 August 1991 to 18 August 1995.
 
(e) Information on Aran is derived from Aran's annual report and accounts for
    the year ended 31 December 1994 and the annual report on Form 20-F filed
    with the SEC for the year ended 31 December 1994.
 
(f) The value of recent transactions relating to the Alba and Gryphon fields
    refers to the following public information:
 
<TABLE>
<CAPTION>
      Date of              %
      Transaction   Interest      Field           Parties                        Price
      <S>           <C>         <C>        <C>               <C>
      July 95           15.5       Alba         Oryx sale                      approx. 
                                           to Union Texas                 $270 million

      July 95           10.0    Gryphon        Clyde sale     Stg(Pounds)35.75 million
                                                 to Cairn
</TABLE>
 
                                      56
<PAGE>
 
15. General
 
(a) The proposed acquisition of the whole of the share capital of Aran is not
    expected to have a material impact on the earnings per share for the year
    ending 31 December 1995, or the net tangible assets per share, of ARCO.
 
(b) No agreement, arrangement or understanding (including any compensation
    arrangement) exists between any member of the ARCO Group or any person
    acting in concert with any member of the ARCO Group for the purpose of the
    Offer and any of the directors, recent directors, shareholders or recent
    shareholders of Aran having any connection with or dependence on, or which
    is conditional on the outcome of, the Offer.
 
(c) There is no agreement, arrangement or understanding whereby beneficial
    ownership of any of the Aran shares acquired pursuant to the Offer will be
    transferred to any other person, save that ARCO Irish Holdings reserves
    the right to transfer any such Aran shares to any member of the ARCO
    Group.
 
(d) The expenses of or incidental to the Offer and the preparation and
    circulation of this document and related documentation are payable by ARCO
    Irish Holdings.
 
(e) Neither ARCO nor any of its subsidiaries including ARCO Irish Holdings has
    entered into a contract outside the ordinary course of business during the
    period beginning two years before the commencement of the Offer period
    which was or may have been material in the context of the ARCO Group.
 
16. Documents Available for Inspection
 
Copies of the documents referred to below will be available for inspection at
the offices of A&L Goodbody, 1 Earlsfort Centre, Hatch Street, Dublin 2 and at
the offices of Clifford Chance at 200 Aldersgate Street, London, EC1A 4JJ,
during normal business hours on any weekday (Saturdays and public holidays
excepted) while the Offer remains open for acceptance:
 
(a) the By-Laws and Certificate of Incorporation of ARCO and ARCO Irish
    Holdings;
 
(b) the Memorandum and Articles of Association of Aran;
 
(c) the published consolidated audited financial statements of ARCO for each
    of the financial years ended 31 December 1993 and 1994 and the report on
    form 10-Q for six months ended 30 June 1995;
 
(d) the published consolidated audited financial statements of Aran for each
    of the financial years ended 31 December 1993 and 1994; and
 
(e) this document and the Acceptance Forms.
 
In addition, ARCO and ARCO Irish Holdings will file with the SEC on 25 August
1995 a Schedule 14D-1 pursuant to the US Exchange Act, together with exhibits,
furnishing certain additional information with respect to the Offer, and may
file amendments thereto. Such Schedule 14D-1 and any amendments thereto,
including exhibits, should be available for inspection and copies should be
obtainable in the manner set forth in paragraph 4 of Appendix 2 (except that
such material will not be available at the regional offices of the SEC).
 
                                      57
<PAGE>
 
APPENDIX 5
 
Certain Provisions of the Irish Companies Act
 
204. Power to Acquire Shares of Shareholders Dissenting from Scheme or
     Contract which has been Approved by Majority.
 
(1) Subject to subsection (2), where a scheme, contract or offer involving the
    acquisition by one company, whether a company within the meaning of this
    act or not (in this section referred to as "the transferee company") of
    the beneficial ownership of all the shares (other than shares already in
    the beneficial ownership of the transferee company) in the capital of
    another company, being a company within the meaning of this Act (in this
    section referred to as "the transferor company") has become binding or
    been approved or accepted in respect of not less than four-fifths in value
    of the shares affected not later than the date 4 months after publication
    generally to the holders of the shares affected of the terms of such
    scheme, contract or offer, the transferee company may at any time before
    the expiration of the period of 6 months next following such publication
    give notice in the prescribed manner to any dissenting shareholder that it
    desires to acquire the beneficial ownership of his shares, and when such
    notice is given the transferee company shall, unless on an application
    made by the dissenting shareholder within one month from the date on which
    the notice was given, the court thinks fit to order otherwise, be entitled
    and bound to acquire the beneficial ownership of those shares on the terms
    on which under the scheme, contract or offer, the beneficial ownership of
    the shares in respect of which the scheme, contract or offer has become
    binding or been approved or accepted is to be acquired by the transferee
    company.
 
(2) Where shares in the transferor company are, at the date of such
    publication, already in the beneficial ownership of the transferee company
    to a value greater than one-fifth of the aggregate value of those shares
    and the shares affected, subsection (1) shall not apply unless the
    assenting shareholders besides holding not less than four-fifths in value
    of the shares affected are not less than three-fourths in number of the
    holders of those shares.
 
(3) For the purpose of this section, shares in the transferor company in the
    beneficial ownership of a subsidiary of the transferee company shall be
    deemed to be in the beneficial ownership of the transferee company, the
    acquisition of the beneficial ownership of shares in the transferor
    company by a subsidiary of the transferee company shall be deemed to be
    the acquisition of such beneficial ownership by the transferee company and
    shares shall not be treated as not being in the beneficial ownership of
    the transferee company merely by reason of the fact that those shares are
    or may become subject to a charge in favour of another person.
 
(4) Where, in consequence of any such scheme, contract or offer, the
    beneficial interest in shares in the transferor company is acquired by the
    transferee company and as a result of such acquisition the transferee
    company has become the beneficial owner of four-fifths in value of all the
    shares in the transferor company then--
 
   (a) the transferee company shall, within one month of the date of such
       acquisition, give notice of that fact in the prescribed manner to all
       holders of shares in the transferor company not in the beneficial
       ownership of the transferee company; and
 
   (b) any such holder may, within 3 months from the giving of the notice to
       him, require the transferee company to acquire his shares:
 
and, where a shareholder gives notice under paragraph (b) in relation to any
shares, the transferee company shall be entitled and bound to acquire the
beneficial ownership of those shares on the terms on which under the scheme,
contract or offer the beneficial ownership of the shares of the assenting
shareholders was acquired by it, or on such other terms as may be agreed or as
the court on the application either of the transferee company or of a
shareholder thinks fit to order, and subsections (5), (6) and (7) shall be
applicable mutatis mutandis as if any reference therein to a notice given
under subsection (1) were a reference to a notice given under paragraph (b).
 
(5) Where a notice has been given by the transferee company under subsection
    (1) and the court has not, on application made by the dissenting
    shareholder, ordered to the contrary, the transferee company shall, on the
    expiration of one month from the date on which the notice was given, or,
    if an application to the court by the dissenting shareholder is then
    pending after that application has been disposed of, transmit to the
    transferor company a copy of the notice together with an instrument of
    transfer of the shares of the dissenting shareholder executed on behalf of
    the dissenting shareholder as transferor by any person appointed to the
    transferee company and by the transferee (being either the transferee
    company or a subsidiary of the transferee company
 
                                      58
<PAGE>
 
     or a nominee of the transferee company or of such a subsidiary) and pay to
     or vest in the transferor company the amount of other consideration
     representing the price payable by the transferee company for the shares
     the beneficial ownership of which by virtue of this section the transferee
     company is entitled to acquire, and the transferor company shall thereupon
     register as the holder of those shares the person who executed such
     instrument as the transferee, so however, that an instrument of transfer
     shall not be so required for any share for which a share warrant is for
     the time being outstanding.
 
(6)  Any sums received by the transferor company under this section shall be
     paid into a separate bank account and any such sums and any other
     consideration so received shall be held by that company on trust for the
     several persons entitled to the shares in respect of which the said sums
     or other consideration were respectively received.
 
(7)  The transferor company or a nominee of the transferor company shall not be
     entitled to exercise any right of voting conferred by any shares in the
     transferee company issued to it or to its nominee as aforesaid except by
     and in accordance with instructions given by the shareholder in respect of
     whom those shares were so issued or his successor in title.
 
(8)  In this section, "the shares affected" means the shares the acquisition of
     the beneficial ownership of which by the transferee company is involved in
     the scheme, contract or offer, "assenting shareholder" means a holder of
     any of the shares affected in respect of which the scheme, contract or
     offer has become binding or been approved or accepted and "dissenting
     shareholder" means a holder of any of the shares affected in respect of
     which the scheme, contract or offer has not become binding or been
     approved or accepted or who has failed or refused to transfer his shares
     in accordance with the scheme, contract or offer.
 
(9)  Where the scheme, contract or offer becomes binding on or is approved or
     accepted by a person in respect of a part only of the shares held by him,
     he shall be treated as an assenting shareholder as regards that part of
     his holding and as a dissenting shareholder as regards the remainder of
     his holding.
 
(10) Where the scheme, contract or offer provides that an assenting
     shareholder may elect between 2 or more sets of terms for the acquisition
     by the transferee company of the beneficial ownership of the shares
     affected, the notice given by the transferee company under subsection (1)
     shall be accompanied by or embody a notice stating the alternative sets
     of terms between which assenting shareholders are entitled to elect and
     specifying which of those sets of terms shall be applicable to the
     dissenting shareholder if he does not before the expiration of 14 days
     from the date of the giving of the notice notify to the transferee
     company in writing his election as between such alternative sets of
     terms, and the terms upon which the transferee company shall under this
     section be entitled and bound to acquire the beneficial ownership of the
     shares of the dissenting shareholder shall be the set of terms which the
     dissenting shareholder shall so notify or, in default of such
     notification, the set of terms so specified as applicable.
 
(11) In the application of this section to a transferor company the share
     capital of which consists of two or more classes of shares, references to
     the shares in the capital of the transferor company shall be construed as
     references to the shares in its capital of a particular class.
 
(12) Subject to subsection (13), this section shall not apply to a scheme,
     contract or offer the terms of which were published generally to the
     holders of the shares affected before the operative date and section 8 of
     the Companies Act, 1959, shall continue to apply to any such scheme,
     contract or offer and for the purposes of any such scheme, contract or
     offer, the said section shall be deemed to remain in full force.
 
(13) Where any such scheme, contract or offer as is mentioned in subsection
     (1) was approved or accepted in the manner described in that subsection
     at any time before the passing of the Companies Act, 1959, the court may
     by order on an application made to it by the transferee company within 6
     months after the operative date authorise notice to be given under this
     section within such time after the making of the order as the court shall
     direct, and this section shall apply accordingly, except that the terms
     on which the shares of the dissenting shareholder are to be acquired
     shall be such terms as the court may by the order direct, instead of the
     terms provided by the scheme, contract or offer.
 
                                      59
<PAGE>
 
Definitions
 
The following definitions apply throughout this document, the Form of
Acceptance and the Letter of Transmittal unless the context requires
otherwise:
 
"Acceptance Condition"         the condition of the Offer as to acceptances
                               set out in condition (a) of Part A of Appendix
                               1
 
"Acceptance Forms"             the Form of Acceptance and, with respect to
                               Aran ADS holders only, the Letter of
                               Transmittal and the Notice of Guaranteed
                               Delivery accompanying this document pursuant
                               to the Offer
 
"Acquisition"                  the proposed acquisition by ARCO Irish
                               Holdings of all the Aran shares (including
                               Aran shares represented by Aran ADSs) pursuant
                               to the Offer
 
"Aran ADRs"                    American Depositary Receipts evidencing
                               interests in Aran ADSs
 
"Aran ADSs"                    American Depositary Shares of Aran each
                               representing 30 Aran shares
 
"Aran"                         Aran Energy plc
 
"Aran Group"                   Aran and its subsidiary and associated
                               undertakings (as defined in the European
                               Communities (Group Accounts: Companies)
                               Regulations, 1992 of Ireland)
 
"Aran securities"              Aran shares and Aran ADSs
 
"Aran securityholders"         holders of Aran securities
 
"Aran shareholders"            holders of Aran shares
 
"Aran shares"                  the existing issued and fully paid ordinary
                               shares of IR20p each in Aran and any further
                               such shares unconditionally allotted or issued
                               while the Offer remains open for acceptance
 
"Aran share option scheme(s)"  any and all share option schemes operated by
                               Aran pursuant to which options to acquire Aran
                               shares have been granted or may be granted
                               during the pendency of the Offer
 
"ARCO"                         Atlantic Richfield Company
 
"ARCO Group"                   ARCO and its subsidiaries, ventures and
                               partnerships in which a controlling interest
                               is held, interests in undivided interest
                               pipeline companies and joint venture companies
                               and its equity interests in certain ventures
                               and partnerships in which less than a
                               controlling interest is held, as consolidated
                               for accounting purposes in the audited
                               financial statements of ARCO
 
"ARCO Irish Holdings"          ARCO Irish Holdings Inc.
 
"Book-Entry Transfer Facility" each of the Depository Trust Company, the
                               Midwest Securities Trust Company and the
                               Philadelphia Depository Trust Company, who are
                               collectively referred to as the "Book-Entry
                               Transfer Facilities"
 
"City Code"                    The City Code on Takeovers and Mergers
 
"Eligible Institution"         a financial institution which is a participant
                               in the Securities Transfer Agents Medallion
                               Program, the New York Stock Exchange Medallion
                               Program, or the Stock Exchanges Medallion
                               Program
 
"Form of Acceptance"           the Form of Acceptance, Authority and Election
                               relating to the Offer for use by holders of
                               Aran shares
 
"Hoare Govett"
                               Hoare Govett Corporate Finance Limited
 
"IR(Pounds)"
                               Irish pounds, being the lawful currency of the
                               Republic of Ireland
 
                                      60
<PAGE>
 
"IRp"                           Irish pence
 
"Ireland"                       Republic of Ireland
 
"Irish Companies Act"           the Companies Act, 1963 of the Republic of
                                Ireland, as amended
 
"Irish Receiving Agent"         AIB Bank, Registrars' & New Issue Department
 
"Irish Stock Exchange"          the Irish Unit of the London Stock Exchange
 
"London Stock Exchange"         the International Stock Exchange of the United
                                Kingdom and the Republic of Ireland Limited
 
"Letter of Transmittal"         the Letter of Transmittal relating to the
                                Offer for use by holders of Aran ADSs
 
"Minimum Acceptance Condition"  the requirement of the City Code (contained in
                                the Acceptance Condition of the Offer) that,
                                in order for the Offer to become unconditional
                                as to acceptances, ARCO Irish Holdings and/or
                                its wholly owned subsidiaries shall have
                                acquired or agreed to acquire pursuant to the
                                Offer or otherwise, Aran shares (including
                                Aran shares represented by Aran ADSs) carrying
                                more than 50 per cent. of the voting rights
                                normally exercisable at general meetings of
                                Aran
 
"NASDAQ"                        the electronic securities market operated by
                                the NASDAQ Stock Market, Inc.
 
"Notice of Guaranteed Delivery" the Notice of Guaranteed Delivery relating to
                                the Offer for use by holders of Aran ADSs
 
"Offer"                         the cash offer contained in this document by
                                Rothschilds on behalf of ARCO Irish Holdings
                                to acquire all the Aran shares including Aran
                                shares represented by Aran ADSs
 
"Panel"                         the Panel on Takeovers and Mergers in the UK
 
"Riada"                         Riada Corporate Finance Limited
 
"Rothschilds"                   N M Rothschild & Sons Limited
 
"$"                             US dollars, being the lawful currency of the
                                United States of America
 
"SEC"                           US Securities and Exchange Commission
 
"Stg(Pounds)"                   Pounds sterling, being the lawful currency of
                                the United Kingdom
 
"Stgp"                          Sterling pence
 
"UK" or "United Kingdom"        the United Kingdom of Great Britain and
                                Northern Ireland
 
"UK Receiving Agent"            The Royal Bank of Scotland plc, Registrar's
                                Department, New Issues Section
 
"US" or "United States"         the United States of America, its possessions
                                and territories, all areas subject to its
                                jurisdiction or any subdivision thereof, any
                                State of the United States and the District of
                                Columbia
 
"US Business Day"               any day other than a Saturday, Sunday or US
                                federal holiday and consists of the time
                                period from 12.01 a.m. through 12.00 midnight,
                                New York City time
 
"US Dealer Manager"             Rothschild Inc. in its capacity as dealer
                                manager for the Offer in the United States
 
 
                                      61
<PAGE>
 
"US Depositary"                First Chicago Trust Company of New York in its
                               capacity as depositary for the Offer in the US
 
"US Exchange Act"              the US Securities Exchange Act of 1934, as
                               amended, and the rules and regulations
                               promulgated thereunder
 
"US HSR Act"                   the US Hart-Scott-Rodino Antitrust
                               Improvements Act of 1976, as amended
 
"US Securities Act"            the US Securities Act of 1933, as amended, and
                               the rules and regulations promulgated
                               thereunder
 
"Wider Aran Group"             Aran and any of its subsidiaries and any
                               company in which Aran has a substantial
                               interest
 
                                      62
<PAGE>
 
Acceptances in respect of Aran Shares
 
Duly completed Forms of Acceptance, accompanied by Aran share certificates
and/or other documents of title, should be delivered to the Irish Receiving
Agent or the UK Receiving Agent at one of the addresses set out below or to the
US Depositary at one of the addresses set out below under acceptances in
respect of Aran ADSs.
 
  The Irish Receiving Agent for the           The UK Receiving Agent for the 
              Offer is:                               Offer is:
 
 
              AIB Bank                       The Royal Bank of Scotland plc
 Registrars' & New Issue Department              Registrar's Department 
             Bankcentre                            New Issues Section 
            P.O. Box 954                            P.O. Box No 859 
            Ballsbridge                              Consort House
             Dublin 4                                 East Street 
                                                       Bedminster 
                                                        Bristol 
                                                        BS99 IXZ
 
        For Information Call:                    For Information Call:
 
 
      01 660 0311 (Ext. 12280)                       0117 937 0666
 
Acceptances in respect of Aran ADSs
 
Manually signed facsimile copies of the Letter of Transmittal will be accepted.
The duly completed Letter of Transmittal, Aran ADRs and any other required
documents should be sent or delivered by each holder of Aran ADSs or his
broker, dealer commercial bank, trust company or other nominee to the US
Depositary at one of its addresses set out below.
 
The US Depositary for the Offer is:
 
                         First Chicago Trust Company 
                                  of New York
 
     By Mail:            For Information Call:     By Hand or Overnight Courier:

 First Chicago Trust  (800) 659 6111 (TOLL FREE)   First Chicago Trust Company 
 Company of New York             or                       of New York 
     Suite 4660            (201) 324 0137                 Suite 4680
   P.O. Box 2559                                        14 Wall Street 
Jersey City, NJ 07303                                    Eighth Floor
                                                      New York, NY 10005


 
 
Any questions or requests for assistance or additional copies of this document,
the Letter of Transmittal and the Notice of Guaranteed Delivery or the Forms of
Acceptance may be directed to the US Depositary, the Irish Receiving Agent or
the UK Receiving Agent at their respective addresses and telephone numbers set
out above. You may also contact your appropriately advised local broker,
dealer, commercial bank or trust company or other nominee for assistance
concerning the Offer.
 
The financial adviser to ARCO and ARCO Irish Holdings is:
                                            
   N M Rothschild & Sons Limited            
             New Court                      
        St. Swithin's Lane                  
          London EC4P 4DU                   


The US Dealer Manager for the Offer is: 
                                
         Rothschild Inc.         
   1251 Avenue of the Americas   
            51st Floor           
       New York, NY 10020        


                                      63

<PAGE>
 
 
                   Printed by RR Donnelley Financial, 13823p

<PAGE>

                                                                EXHIBIT 99(a)(2)
 
THIS DOCUMENT IS IMPORTANT AND REQUIRES YOUR IMMEDIATE ATTENTION. If you are
in any doubt about the action you should take, you are recommended to seek
advice from your own appropriately authorized independent financial advisor.
 
N M Rothschild & Sons Limited ("Rothschilds") is acting for Atlantic Richfield
Company ("ARCO") and ARCO Irish Holdings Inc. ("ARCO Irish Holdings") in
relation to the Offer and no one else, and will not be responsible to anyone
other than ARCO and ARCO Irish Holdings for providing the protections afforded
to customers of Rothschilds nor for providing advice in relation to the Offer.
Rothschilds is acting through Rothschild Inc. for the purpose of making the
Offer in the United States.
 
If you have sold or otherwise transferred all your American Depositary Shares
("Aran ADSs") of Aran Energy plc ("Aran"), please pass this document and all
accompanying documents as soon as possible to the purchaser or transferee, or
to the bank, stockbroker or other agent through whom the sale or transfer was
effected for transmission to the purchaser or transferee. However, such
documents should not be distributed, forwarded or transmitted in or into
Australia, Canada or Japan.
 
This Letter should be read in conjunction with the accompanying offer document
dated August 25, 1995 (the "Offer Document"). The definitions used in the
Offer Document also apply, where the context requires, in this Letter.
 
-------------------------------------------------------------------------------
 
                             LETTER OF TRANSMITTAL
 
              TO ACCEPT THE OFFER FOR AMERICAN DEPOSITARY SHARES
                   EVIDENCED BY AMERICAN DEPOSITARY RECEIPTS
 
                                      OF
 
                                ARAN ENERGY PLC
 
             PURSUANT TO THE OFFER DOCUMENT DATED AUGUST 25, 1995
 
                                      BY
 
                         N M ROTHSCHILD & SONS LIMITED
 
                                 ON BEHALF OF
 
                           ARCO IRISH HOLDINGS INC.
 
                      (A WHOLLY OWNED SUBSIDIARY OF ARCO)
 
 THE OFFER IS OPEN FOR ACCEPTANCE UNTIL 3:00 P.M. (DUBLIN AND LONDON TIME),
 10:00 A.M. (NEW YORK CITY TIME), ON SEPTEMBER 23, 1995 (THE "INITIAL
 PERIOD"), UNLESS EXTENDED (IN ACCORDANCE WITH THE TERMS THEREOF). AT THE
 CONCLUSION OF THE INITIAL PERIOD OR ON OR BEFORE THE CONCLUSION OF ANY
 EXTENSION THEREOF AND ON THE SATISFACTION OR, WHERE PERMITTED, WAIVER OF
 THE CONDITION(S) TO THE OFFER, THE PURCHASE OF ALL SECURITIES IN RESPECT
 OF WHICH THE OFFER HAS BEEN VALIDLY ACCEPTED AND NOT WITHDRAWN WILL TAKE
 PLACE AND THE OFFER WILL BE EXTENDED FOR A SUBSEQUENT PERIOD OF AT LEAST
 FOURTEEN CALENDAR DAYS. PRIOR TO THE OFFER BECOMING OR OTHERWISE BEING
 DECLARED UNCONDITIONAL IN ALL RESPECTS, ACCEPTING ARAN SECURITYHOLDERS
 WILL HAVE THE RIGHT TO WITHDRAW THEIR ACCEPTANCES IN RESPECT THEREOF.
 HOWEVER, IN THE EVENT OF THE OFFER BECOMING OR BEING DECLARED
 UNCONDITIONAL IN ALL RESPECTS, NO RIGHTS OF WITHDRAWAL WILL BE AVAILABLE
 TO ACCEPTING ARAN SECURITYHOLDERS IN THE SUBSEQUENT PERIOD DURING WHICH
 THE OFFER REMAINS OPEN FOR ACCEPTANCE.
 
 
                  TO: FIRST CHICAGO TRUST COMPANY OF NEW YORK
                                 US DEPOSITARY          
<TABLE> 
<S>                       <C>                                     <C> 
        By Mail:              By Facsimile Transmission           By Hand or Overnight Courier:
      Suite 4660          (for Eligible Institutions only):                  Suite 4680
    P.O. Box 2559            Fax: (201) 222-4720 or 4721                   14 Wall Street
Jersey City, NJ 07303                                                       Eighth Floor
                                                                         New York, NY 10005
                             For Information Call:
                                             
                          (800) 659-6111 (Toll Free)
                                      or
                                (201) 324 0137
</TABLE> 
<PAGE>
 
   DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS, OR TRANSMISSION OF
INSTRUCTIONS VIA A FACSIMILE OR TELEX NUMBER, OTHER THAN AS SET FORTH ABOVE,
DOES NOT CONSTITUTE A VALID DELIVERY.
 
   THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.
 
   ACCEPTING HOLDERS OF ARAN ADSs WILL RECEIVE PAYMENT IN DOLLARS INSTEAD OF
IRISH POUNDS UNLESS THEY ELECT OTHERWISE HEREIN TO RECEIVE PAYMENT IN IRISH
POUNDS OR POUNDS STERLING. IF YOU WISH TO RECEIVE IRISH POUNDS INSTEAD OF
DOLLARS YOU MUST PLACE A "X" IN THE BOX ENTITLED "IRISH POUNDS PAYMENT
ELECTION." IF YOU WISH TO RECEIVE POUNDS STERLING INSTEAD OF DOLLARS YOU MUST
PLACE A "X" IN THE BOX ENTITLED "POUNDS STERLING PAYMENT ELECTION."
 
   ACCEPTANCE OF THE OFFER IN RESPECT OF ARAN SHARES (EXCEPT INSOFAR AS THEY
ARE REPRESENTED BY ARAN ADSs) CANNOT BE MADE BY MEANS OF THIS LETTER OF
TRANSMITTAL. If you hold Aran shares that are not represented by Aran ADSs,
you can obtain a Form of Acceptance for accepting the Offer in respect of
those Aran shares from the Irish Receiving Agent, the US Depositary and the UK
Receiving Agent. See Instruction 13 of this Letter of Transmittal.
 
   Delivery of a Letter of Transmittal, Aran American Depositary Receipts
evidencing Aran ADSs ("Aran ADRs") (or book-entry transfer of such Aran ADSs)
and any other required documents to the US Depositary by Aran ADSs holders
will be deemed (without any further action by the US Depositary) to constitute
an acceptance of the Offer by such holder with respect to such Aran ADSs
subject to the terms and conditions set out in the Offer Document, and this
Letter of Transmittal. Capitalised terms and certain other terms used in this
Letter of Transmittal and not otherwise defined herein shall have the
respective meanings assigned to them in the Offer Document.
 
   This Letter of Transmittal is to be used either if Aran ADRs evidencing
Aran ADSs are to be forwarded herewith or if delivery of Aran ADSs is to be
made by book-entry transfer to an account maintained by the US Depositary at a
Book-Entry Transfer Facility as defined in and pursuant to the procedures for
book-entry transfer set forth in "Acceptance procedures for holders of Aran
ADSs--Book-Entry Transfer Facilities" in Part B of Appendix 1 to the Offer
Document. Holders of Aran ADSs who deliver a Notice of Guaranteed Delivery to
accept the Offer must, inter alia, effect the deliveries described below
within three trading days after the execution of such Notice.
 
[_]  CHECK BOX IF ARAN ADSs IN RESPECT OF WHICH THE OFFER IS BEING ACCEPTED ARE
     BEING DELIVERED BY BOOK-ENTRY TRANSFER MADE TO AN ACCOUNT MAINTAINED BY
     THE US DEPOSITARY WITH A BOOK-ENTRY TRANSFER FACILITY AND COMPLETE THE
     FOLLOWING (ONLY PARTICIPANTS IN A BOOK-ENTRY TRANSFER FACILITY MAY DELIVER
     ARAN ADSs BY BOOK-ENTRY TRANSFER):
 
     Name of Delivering Institution ____________________________
 
     Check box opposite name of relevant Book-Entry Transfer Facility:
 
     [_]  The Depositary Trust Company
 
     [_]  Midwest Securities Trust Company
 
     [_]  Philadelphia Depositary Trust Company
 
     Account Number __________       Transaction Code Number ____________
 
     If a holder of Aran ADSs wishes to accept the Offer and Aran ADRs
evidencing such ADSs are not immediately available or the procedures for book-
entry transfer cannot be completed on a timely basis, or if time will not
permit all required documents to reach the US Depositary prior to the expiry
of the Offer, such holder's acceptance of the Offer may nevertheless be
effected using the guaranteed delivery procedures. See "Acceptance procedures
for holders of Aran ADSs--Guaranteed delivery procedures" in Part B of
Appendix 1 to the Offer Document. See Instruction 2 of this Letter of
Transmittal. HOWEVER, RECEIPT OF A NOTICE OF GUARANTEED DELIVERY WILL NOT BE
TREATED AS A VALID ACCEPTANCE FOR THE PURPOSE OF SATISFYING THE ACCEPTANCE
CONDITION.
 
[_]  CHECK BOX ONLY IF ARAN ADSs IN RESPECT OF WHICH THE OFFER IS BEING
     ACCEPTED ARE BEING DELIVERED PURSUANT TO A NOTICE OF GUARANTEED DELIVERY
     PREVIOUSLY SENT TO THE US DEPOSITARY AND COMPLETE THE FOLLOWING:
 
     Name(s) of registered owner(s) ____________________
<PAGE>
 
   Date of execution of notice of Guaranteed Delivery _________________________
 
   Name of Institution that guaranteed delivery ______
 
   IF DELIVERY BY BOOK-ENTRY TRANSFER CHECK BOX:
 
   [_] The Depository Trust Company
   [_] Midwest Securities Trust Company
   [_] Philadelphia Depository Trust Company
 
   Account Number __________       Transaction Code ________
 
                      DESCRIPTION OF ACCEPTING ARAN ADSs
<TABLE> 
<CAPTION> 
-------------------------------------------------------------------------------
  NAME(S) AND ADDRESS(ES) OF                                       ACCEPTING ARAN ADSs
  REGISTERED HOLDER(S) (PLEASE FILL IN,                   (ATTACH ADDITIONAL LIST IF NECESSARY)
  IF BLANK)
-----------------------------------------------------------------------------------------------------------
  <S>                                     <C>                    <C>                    <C>
                                          ACCEPTING ARAN ADR     TOTAL NUMBER OF        NUMBER OF ACCEPTING
                                          SERIAL NUMBER(S)*      ACCEPTING ARAN ADSs    ARAN ADSs**
                                                                 EVIDENCED BY ADRs*
-----------------------------------------------------------------------------------------------------------
</TABLE>
 *   Need not be completed by Book-Entry Securityholders.
 **  Unless otherwise indicated, it will be assumed that the Offer is being
     accepted in respect of all Aran ADSs delivered to the US Depositary.
     See Instruction 4.
 
                    NOTE: SIGNATURES MUST BE PROVIDED BELOW
              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY
 
Ladies and Gentlemen:
 
   The undersigned hereby instructs the US Depositary to accept the Offer on
behalf of the undersigned with respect to the Aran ADSs (which expression in
this Letter of Transmittal shall, except where the context otherwise requires,
be deemed to include, without limitation, the Aran shares represented thereby)
specified in the box entitled "Description of Accepting Aran ADSs" subject to
the terms and conditions set forth in the Offer Document and this Letter of
Transmittal, by informing ARCO Irish Holdings in writing that the Offer has
been so accepted. The undersigned hereby acknowledges that delivery of this
Letter of Transmittal, the Aran ADSs evidencing tendered Aran ADSs (or book-
entry transfer of such Aran ADSs) and any other required documents to the US
Depositary by a holder of Aran ADSs will be deemed (without any further action
by the US Depositary) to constitute acceptance of the Offer by such holder in
respect of such holder's Aran ADSs, subject to the terms and conditions set
out in the Offer Document and this Letter of Transmittal.
 
   The undersigned understands that acceptance of the Offer by the undersigned
pursuant to the procedures described herein and in the instructions hereto
will constitute a binding agreement between the undersigned and ARCO Irish
Holdings upon the terms and subject to the conditions of the Offer. IF
ACCEPTANCE HAS BEEN MADE IN RESPECT OF THE ARAN ADSs THEN A SEPARATE
ACCEPTANCE IN RESPECT OF THE ARAN SHARES REPRESENTED BY SUCH ARAN ADSs MAY NOT
BE MADE.
 
   The undersigned hereby delivers to the US Depositary the above-described
Aran ADSs for which the Offer is being accepted, in accordance with the terms
and conditions of the Offer Document and this Letter of Transmittal, receipt
of which is hereby acknowledged.
 
   Upon the terms of the Offer (including, if the Offer is extended, revised
or amended, the terms or conditions of any such extension, revision or
amendment), and effective at the time that the conditions to the Offer have
been satisfied or, where permitted, waived (at which time ARCO Irish Holdings
will give notice thereof to the US Depositary), the undersigned hereby sells,
assigns and transfers to, or upon the order of, ARCO Irish Holdings all right,
title and interest in and to all Aran ADSs with respect to which the Offer is
being accepted (and any and all Aran ADSs or other securities or rights
issuable in respect of such Aran ADSs) and irrevocably constitutes and
appoints the US Depositary the true and lawful agent and attorney-in-fact of
the undersigned with respect to such
<PAGE>
 
Aran ADSs (and any such other Aran ADSs, securities or rights), with full
power of substitution (such power of attorney being deemed to be an
irrevocable power coupled with an interest), to (a) deliver ADRs for such Aran
ADSs (and any such other Aran ADSs, securities or rights) or accept transfer
of ownership of such Aran ADSs (and any such other Aran ADSs, securities or
rights) on the account books maintained by a Book-Entry Transfer Facility
together, in any such case, with all accompanying evidences of transfer and
authenticity to, or upon the order of, ARCO Irish Holdings, (b) present such
Aran ADRs (and any other Aran ADSs, securities or rights) for transfer, and
(c) receive all benefits and otherwise exercise all rights of beneficial
ownership of such Aran ADSs (and any such other Aran ADSs, securities or
rights), all in accordance with the terms of the Offer.
 
   The undersigned agrees that its execution hereof (together with any
signature guarantees) and its delivery to the US Depositary shall constitute
an authority to any director of ARCO Irish Holdings or Rothschilds and to ARCO
Irish Holdings or Rothschilds and/or their respective agents in accordance
with the terms of Section 7 of Part B of Appendix l of the Offer Document
(Revised Offer and reduction of the Acceptance Condition).
 
   The undersigned agrees that effective from and after the date hereof or, if
later, the date on which the Offer becomes unconditional (or if the Offer will
become unconditional or lapse immediately upon the outcome of the resolution
in question or in such other circumstances as ARCO Irish Holdings may request
and the Panel may permit), (a) ARCO Irish Holdings or its agents shall be
entitled to direct the exercise of any votes attaching to the Aran Shares
represented by any Aran ADSs in respect of which the Offer has been accepted
or is deemed to have been accepted (the "Accepted ADSs") and any or all other
rights and privileges attaching to such Aran ADSs, including any right to
requisition the convening of a general meeting or separate class meeting of
Aran, and (b) the execution of this Letter of Transmittal by a holder of Aran
ADSs (together with any signature guarantees) and its delivery to the US
Depositary shall constitute in respect of Accepted ADSs (i) an authority to
Aran or its agents from the undersigned to send any notice, circular, warrant,
document or other communications that may be required to be sent to him or her
as an Aran ADS holder to ARCO Irish Holdings at its principal office, (ii) an
authority to ARCO Irish Holdings or any director of ARCO Irish Holdings or any
person appointed by such person for such purpose to sign any consent to short
notice of a general meeting or separate class meeting on behalf of the holder
of Accepted ADSs and/or to execute a form of proxy in respect of the Accepted
ADSs appointing any person nominated by ARCO Irish Holdings to attend general
meetings and separate class meetings of Aran and any adjournment thereof and
to exercise the votes attaching to the Aran shares represented by such
Accepted ADSs on his or her behalf, such votes to be cast (where relevant) so
far as possible to satisfy or to assist directly or indirectly in satisfying
any outstanding condition of the Offer, (iii) the agreement of the undersigned
not to exercise any such rights without the consent of ARCO Irish Holdings and
the irrevocable undertaking of the undersigned not to appoint a proxy for or
to attend general meetings or separate class meetings of Aran in respect of
such Accepted ADSs, (iv) confirmation that the undersigned (1) has not
received or sent copies of this Letter of Transmittal or any related document
in, into or from Australia, Canada or Japan; (2) is accepting the Offer from
outside Australia, Canada and Japan; and (3) is not an agent or fiduciary
acting on a non-discretionary basis for a principal, unless such agent or
fiduciary is an authorised employee of such principal or such principal has
given any instructions with respect to the Offer from outside Australia,
Canada and Japan and (4) confirmation that the undersigned is entitled to sell
and transfer the beneficial ownership of the Accepted ADSs and that such
Accepted ADSs are sold fully paid and free from all liens, equitable
interests, charges, and encumbrances and together with all rights attaching
thereto since (and including) August 21, 1995 including voting rights and the
right to all dividends and other distributions declared, made or paid on or
after August 21, 1995.
 
   The undersigned hereby represents and warrants that the undersigned has
full power and authority to accept the Offer and to sell, assign and transfer
the Aran ADSs (and the Aran shares represented by such Aran ADSs) in respect
of which the Offer is being accepted or deemed to be accepted (and any and all
other Aran ADSs, securities or rights issued or issuable in respect of such
Aran ADSs) and, when the same are purchased by ARCO Irish Holdings, ARCO Irish
Holdings will acquire good title thereto, free from all liens, equitable
interests, charges, encumbrances and together with all rights attaching
thereto, including voting rights and the right to receive all dividends and
other distributions declared, made or paid after August 21, 1995 with respect
to the Aran shares represented by the Aran ADSs. The undersigned will, upon
request, execute any additional documents deemed by the US Depositary or ARCO
Irish Holdings to be necessary or desirable to complete the sale, assignment
and transfer of the Aran ADSs in respect of which the Offer is being accepted
(and any and all other Aran ADSs, securities or rights).
 
   All authority herein conferred or agreed to be conferred pursuant to this
Letter of Transmittal shall be binding upon the successors, assigns, heirs,
executors, administrators and legal representatives of the undersigned and
shall not be affected by, and shall survive, the death or incapacity of the
undersigned. Except as stated in the Offer Document, this acceptance is
irrevocable.
<PAGE>
 
   Unless otherwise indicated herein under "Special Payment Instructions", the
undersigned hereby instructs the US Depositary to issue, or cause to be
issued, the check for the purchase price and/or return, or cause to be
returned, any Aran ADRs evidencing Aran ADSs in respect of which the Offer is
not being accepted in the name(s) of the registered holder(s) appearing under
"Description of Accepting Aran ADSs". Similarly, unless otherwise indicated
under "Special Delivery Instructions", the undersigned hereby instructs the US
Depositary to mail, or cause to be mailed, the checks for the purchase price
and/or return, or cause to be returned, any Aran ADRs evidencing Aran ADSs in
respect of which the Offer is not being accepted (and accompanying documents,
as appropriate) to the address(es) of the registered holder(s) appearing under
"Description of Accepting Aran ADSs". In the event that the "Special Payment
Instructions" and/or the "Special Delivery Instructions" are completed, the
undersigned hereby instructs the US Depositary to issue and/or mail, or cause
to be issued and/or mailed, the checks for the purchase price, if any, in the
name of, and to, the person or persons so indicated. In the case of a book-
entry delivery of Aran ADSs, the undersigned hereby instructs the US
Depositary to credit the account maintained at the Book-Entry Transfer
Facility indicated above with any Aran ADSs not accepted for payment. The
undersigned recognises that the US Depositary will not transfer any Aran ADSs
from the name of the registered holder thereof if ARCO Irish Holdings does not
accept for payment any of the Aran ADSs so tendered.
 
   If neither the box headed "Irish pounds Payment Election" nor the box
headed "pounds Sterling Payment Election" is checked, the undersigned hereby
instructs the US Depositary to convert all amounts payable pursuant to the
Offer from Irish pounds to U.S. dollars at the noon buying rate in London for
cable transfers prevailing on the latest practicable business day preceding
the dispatch of payment as certified by The Royal Bank of Scotland plc and to
pay such amounts by check payable in U.S. dollars. The actual amount of U.S.
dollars or pounds sterling received will depend upon the exchange rate
prevailing on the latest practicable date preceding the date on which payment
is made by ARCO Irish Holdings. Aran securityholders should also be aware that
the exchange rate which is prevailing at the date on which the undersigned
executes this Letter of Transmittal may be different from that on the date of
despatch of payment by ARCO Irish Holdings. In all cases, fluctuations in the
US dollar/Irish pound and pounds sterling/Irish pounds exchange rates are at
the risk of accepting Aran securityholders who do not elect to receive their
consideration in Irish pounds. Such currency exchange will be effected by the
US Depositary on behalf of the requesting Aran securityholder and ARCO Irish
Holdings shall have no responsibility or obligation with respect thereto.
 
   SUBJECT TO THE TERMS OF THE OFFER DOCUMENT, THIS LETTER OF TRANSMITTAL
SHALL NOT BE CONSIDERED COMPLETE AND VALID, AND PAYMENT OF CONSIDERATION
PURSUANT TO THE OFFER SHALL NOT BE MADE, UNTIL THE ARAN ADRs EVIDENCING THE
ARAN ADSs IN RESPECT OF THE ARAN ADSs IN RESPECT OF WHICH THE OFFER IS BEING
ACCEPTED AND ALL OTHER REQUIRED DOCUMENTATION HAVE BEEN RECEIVED BY THE US
DEPOSITARY AS PROVIDED IN THE OFFER DOCUMENT AND THIS LETTER OF TRANSMITTAL.
<PAGE>
 
 
                                   SIGN HERE
               (ALSO COMPLETE SUBSTITUTE FORM W-9 ON BACK COVER)
     --------------------------------------------------------------

     --------------------------------------------------------------
                           (Signature(s) of Owner(s))
 
     Dated: 
           -------------------------------------------------------- 
     (Must be signed by registered holder(s) exactly as name(s)
     appear(s) on Aran ADR(s) evidencing the Aran ADS(s) or by
     person(s) to whom Aran ADR(s) surrendered have been assigned
     and transferred, as evidenced by endorsement, stock powers
     and other documents transmitted herewith. If signature is by
     any trustee, executor, administrator, guardian, attorney-in-
     fact, officer of a corporation or others acting in a
     fiduciary or representative capacity, please set forth the
     following and see Instruction 5.)

     Name(s) 
            -------------------------------------------------------

     --------------------------------------------------------------
                                 (Please Print)

     Capacity (Full Title) 
                           ----------------------------------------

     Address 
             ------------------------------------------------------

     --------------------------------------------------------------
                              (Including Zip Code)
 
     Area Code and Telephone No. 
                                 ----------------------------------
     Employer Identification No.
     or Social Security No. 
                           ---------------------------------------- 

                           GUARANTEE OF SIGNATURE(S)
                           (SEE INSTRUCTIONS 1 AND 5)

     Authorised Signature 
                          -----------------------------------------
     Name 
          ---------------------------------------------------------
                                 (Please Print)
     Name of Firm 
                  -------------------------------------------------
     Address 
            -------------------------------------------------------

     --------------------------------------------------------------
                              (Including Zip Code)
 
     Area Code and Telephone No. 
                                -----------------------------------
     Dated: 
           --------------------------------------------------------
<PAGE>
 
   [_] CHECK HERE IF ANY OF THE ARAN ADRs REPRESENTING ARAN ADSs THAT YOU
       OWN HAVE BEEN LOST, STOLEN OR DESTROYED AND SEE INSTRUCTION 12.
 
       Number of Aran shares represented by the lost, stolen or destroyed Aran
       ADRs:
 
    SPECIAL PAYMENT INSTRUCTIONS       SPECIAL DELIVERY INSTRUCTIONS
   (SEE INSTRUCTIONS 1, 5, 6           (SEE INSTRUCTIONS 1, 5, 6 
                AND 7)                              AND 7)  
 
 
   [_] Check box ONLY if the check      Check boxes ONLY if the check
   for the purchase price for           for the purchase price for
   Aran ADSs accepted for               Aran ADSs accepted for
   payment is to be issued in           payment and/or the Aran ADRs
   the name of someone other            for any Aran ADSs with
   than the undersigned.                respect to which the Offer is
                                        not being accepted or which
                                        are accepted for payment are
                                        to be sent to someone other
                                        than the undersigned, or to
                                        the undersigned at an address
                                        other than that shown above.
 
 
 
   Name _________________________       Mail [_] Check                  
   (Please Print: First, Middle              [_] ADRs to:               
   and Last Name)                       Name _________________________  
                                        (Please Print: First, Middle    
   Address ______________________       and Last Name)                  
                                                                        
   ------------------------------       Address ______________________  
        (Including Zip Code)                                            
   (Employer Identification or          ------------------------------  
   Social Security No.) _________            (Including Zip Code)       
                                                                         
 
               POUNDS STERLING OR IRISH POUNDS PAYMENT ELECTION
                              (SEE INSTRUCTION 8)
 
                      Check appropriate box below
                      ONLY if you wish to receive
                      all (but not part) of the
                      amounts to be paid by a check
                      or checks in pounds sterling
                      or Irish pounds. If you do
                      not check a box you will
                      receive payment by a check or
                      checks in US dollars. If you
                      check the "Irish pounds
                      Payment Election" box you
                      will receive the Irish pound
                      amounts payable to you. If
                      you do not check either box
                      or you check the "Pounds
                      sterling Payment Election"
                      box ARCO Irish Holdings will
                      arrange for the conversion of
                      the Irish pound amounts
                      payable to you to US dollars
                      or pounds sterling, as the
                      case may be, at the noon
                      buying rate in London for
                      transfers in Irish pounds
                      prevailing on the latest
                      practicable business day
                      preceding the dispatch of
                      payment as certified by The
                      Royal Bank of Scotland plc.
 
                      [_] Pounds sterling Payment
                      Election
 
                      [_] Irish pounds Payment
                      Election
 
<PAGE>
 
                                 INSTRUCTIONS
 
                   FORMING PART OF THE TERMS AND
                   CONDITIONS OF THE OFFER
 
   1. GUARANTEE OF SIGNATURES. No signature guarantee is required on the Letter
of Transmittal if (a) the Letter of Transmittal is signed by the registered
holder(s) of the Aran ADSs in respect of which the Offer is being accepted
herewith and such holder(s) have not completed either the box entitled
"Special Payment Instructions" or the box entitled "Special Delivery
Instructions" on this Letter of Transmittal or (b) such Aran ADSs are accepted
for the account of an Eligible Institution. In all other cases all signatures
on this Letter of Transmittal must be guaranteed by a financial institution
(including most banks, savings and loan associations and brokerage houses)
which is a participant in the Securities Transfer Agents Medallion Program,
the New York Stock Exchange Medallion Program, or the Stock Exchange Medallion
Program (an "Eligible Institution"). See Instruction 5.
 
   If the Aran ADSs are registered in the name of a person other than the
signatory of the Letter of Transmittal, then the Aran ADRs evidencing the Aran
ADSs in respect of which the Offer is being accepted must be endorsed or
accompanied by appropriate stock powers, signed exactly as the name or names
of the registered owner or owners appear on the Aran ADRs, with the signatures
on such Aran ADRs or stock powers guaranteed as aforesaid. See Instruction 5.
 
   2. DELIVERY OF LETTER OF TRANSMITTAL AND ADSs. This Letter of Transmittal is
to be completed by holders either if Aran ADRs evidencing Aran ADSs are to be
forwarded herewith or if delivery is to be made by book-entry transfer to an
account maintained by the US Depositary at a Book-Entry Transfer Facility
pursuant to the procedures for book-entry transfer set out in "Acceptance
procedures for holders of Aran ADSs--Book-Entry Transfer Facilities" in Part B
of Appendix 1 to the Offer Document. Aran ADRs evidencing Aran ADSs or
confirmation of any book-entry transfer into the US Depositary's account at a
Book-Entry Transfer Facility of Aran ADSs delivered electronically, as well as
a properly completed and duly executed Letter of Transmittal (or facsimile
thereof), together with any required signature guarantees and any other
documents required by this Letter of Transmittal, must be delivered to the US
Depositary at one of its addresses set forth herein.
 
   Aran ADS holders whose Aran ADRs are not immediately available or who
cannot deliver their Aran ADRs and all other required documents to the US
Depositary or complete the procedures for book-entry transfer on a timely
basis may accept the Offer prior to the Offer having lapsed or expired with
respect to their Aran ADSs by properly completing and duly executing the
Notice of Guaranteed Delivery pursuant to the guaranteed delivery procedures
set out in "Acceptance procedures for holders of Aran ADSs--Guaranteed
delivery procedures" in Part B of Appendix 1 to the Offer Document. Pursuant
to the guaranteed delivery procedures, such holder's acceptance of the Offer
may nevertheless be effected if all of the following conditions are satisfied:
(a) acceptance is made by or through an Eligible Institution; (b) a properly
completed and duly executed Notice of Guaranteed Delivery substantially in the
form provided by ARCO Irish Holdings is received by the US Depositary, as
provided for in the Offer Document, prior to the Offer having expired; and (c)
the Aran ADRs evidencing the Aran ADSs in respect of which the Offer is being
accepted (or, in the case of Aran ADSs held in book-entry form, timely
confirmation of the book-entry transfer of such Aran ADSs into the US
Depositary's account at a Book-Entry Transfer Facility as described in the
Offer Document) together with a properly completed and duly executed Letter of
Transmittal (or facsimile thereof) with any required signature guarantees and
any other documents required by this Letter of Transmittal, are received by
the US Depositary within three trading days after the date of execution of
such Notice of Guaranteed Delivery. For these purposes, a "trading day" is any
day on which NASDAQ is open for business.
 
   THE NOTICE OF GUARANTEED DELIVERY MAY BE DELIVERED BY HAND TO THE US
DEPOSITARY OR TRANSMITTED BY FACSIMILE TRANSMISSION OR MAILED TO THE US
DEPOSITARY AND MUST INCLUDE A SIGNATURE GUARANTEE BY AN ELIGIBLE INSTITUTION
IN THE FORM SET OUT IN SUCH NOTICE OF GUARANTEE DELIVERY. THE METHOD OF
DELIVERY OF ARAN ADSs AND ALL OTHER REQUIRED DOCUMENTS IS AT THE OPTION AND
RISK OF THE HOLDERS OF ARAN ADSs ACCEPTING THE OFFER. IF DELIVERY IS BY MAIL,
REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS
RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY
DELIVERY.
 
   RECEIPT OF A NOTICE OF GUARANTEED DELIVERY WILL NOT BE TREATED AS A VALID
ACCEPTANCE FOR THE PURPOSE OF SATISFYING THE ACCEPTANCE CONDITION. TO BE
COUNTED TOWARDS SATISFACTION OF THIS CONDITION, PRIOR TO THE OFFER HAVING
EXPIRED THE ARAN ADRs EVIDENCING ARAN ADSs REFERRED TO IN THE NOTICE OF
GUARANTEED DELIVERY MUST HAVE BEEN RECEIVED BY THE US DEPOSITARY OR, IN THE
CASE OF ARAN ADSs HELD IN BOOK-ENTRY FORM, TIMELY CONFIRMATION OF A BOOK-ENTRY
TRANSFER OF SUCH ARAN ADSs INTO THE US DEPOSITARY'S ACCOUNT AT A BOOK-ENTRY
TRANSFER FACILITY PURSUANT TO THE PROCEDURES SET OUT IN THE OFFER DOCUMENT,
MUST HAVE BEEN RECEIVED BY THE US DEPOSITARY, IN EITHER CASE, TOGETHER WITH A
DULY EXECUTED LETTER OF TRANSMITTAL (OR FACSIMILE THEREOF) WITH ANY REQUIRED
SIGNATURE GUARANTEES AND ANY OTHER REQUIRED DOCUMENTS.
 
   No alternative, conditional or contingent acceptance will be accepted and
no fractional Aran ADSs will be purchased. All accepting Aran ADS holders, by
execution of this Letter of Transmittal (or facsimile thereof), waive any
right to receive any notice of the acceptance of their Aran ADSs for payment.
<PAGE>
 
   3. INADEQUATE SPACE. If the space provided herein is inadequate, the serial
numbers of the certificates and/or the number of Aran ADSs should be listed on
a separate schedule attached hereto.
 
   4. PARTIAL ACCEPTANCES (APPLICABLE TO ARAN ADR HOLDERS ONLY). If the Offer
is to be accepted in respect of less than all of the Aran ADSs evidenced by
any Aran ADRs delivered to the US Depositary herewith, fill in the number of
Aran ADSs in respect of which the Offer is being accepted in the box entitled
"Number of Accepting Aran ADSs". In such case, in the event of the Offer
becoming unconditional, a new Aran ADR for the remainder of the Aran ADSs (in
respect of which the Offer is not being accepted) represented by the old Aran
ADR will be sent to the registered holder (or delivered to the person signing
the Letter of Transmittal or in accordance with such person's instructions as
such person properly indicates thereon) as promptly as practicable following
the date on which the Aran ADSs in respect of which the Offer have been
accepted are purchased.
 
   The Offer will be deemed to have been accepted in respect of all Aran ADSs
evidenced by Aran ADRs delivered to the US Depositary unless otherwise
indicated. In the case of partial acceptances, Aran ADSs in respect of which
the Offer was not accepted will not be reissued to a person other than the
registered holder of the released ADR.
 
   5. SIGNATURES ON LETTER OF TRANSMITTAL, STOCK POWERS AND ENDORSEMENTS. If
this Letter of Transmittal is signed by the registered holder(s) of the Aran
ADSs in respect of which the Offer is being accepted hereby, the signature(s)
must correspond with the name(s) as written on the face of the certificates
without any change whatsoever.
 
   If any of the Aran ADSs in respect of which the Offer is being accepted
hereby are owned of record by two or more owners, all such owners must sign
this Letter of Transmittal.
 
   If any of the Aran ADSs in respect of which the Offer is being accepted are
registered in different names on different Aran ADRs, it will be necessary to
complete, sign and submit as many separate Letters of Transmittal as there are
different registrations of Aran ADRs.
 
   If this Letter of Transmittal or any Aran ADRs or stock powers are signed
by trustees, executors, administrators, guardians, attorneys-in-fact, officers
of corporations or others acting in a fiduciary or representative capacity,
such persons should so indicate when signing, and proper evidence satisfactory
to ARCO Irish Holdings of their authority so to act must be submitted.
 
   When this Letter of Transmittal is signed by the registered holder(s) of
the Aran ADSs listed and transmitted hereby, no endorsements of certificates
or separate stock powers are required unless payment of the purchase price is
to be issued to a person other than the registered holder(s). Signatures on
such Aran ADRs or stock powers must be guaranteed by an Eligible Institution.
 
   If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Aran ADSs listed, the Aran ADRs must be endorsed
or accompanied by appropriate stock powers signed exactly as the names(s) of
the registered holder(s) appear(s) on the Aran ADRs evidencing such Aran ADSs.
Signatures on such Aran ADRs or stock powers must be guaranteed by an Eligible
Institution.
 
   6. STOCK TRANSFER TAXES. ARCO Irish Holdings will pay or cause to be paid
any stock transfer taxes with respect to the transfer and sale to it or its
order of Aran ADSs pursuant to the Offer. If, however, payment of the purchase
price is to be made to any persons other than the registered holder(s), or if
Aran ADSs in respect of which the Offer is being accepted are registered in
the name of any person other than the person(s) signing this Letter of
Transmittal, the amount of any stock transfer taxes (whether imposed on the
registered holder(s) or such person(s))payment on account of the transfer to
such person will be deducted from the purchase price unless satisfactory
evidence of the payment of such taxes or exemption therefrom is submitted.
 
   Except as provided in this Instruction 6, it will not be necessary for
transfer tax stamps to be affixed to the Aran ADRs listed in this Letter of
Transmittal.
 
   7. SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS. If the check for the purchase
price and/or any Aran ADRs evidencing Aran ADSs in respect of which the Offer
is not being accepted are to be issued in the name of a person other than the
signer of this Letter of Transmittal or if the check for the purchase price is
to be sent and/or such Aran ADRs are to be returned to a person other than the
signer of this Letter of Transmittal or to an address other than that shown on
the reverse, the boxes labelled "Special Payment Instructions" and/or "Special
Delivery Instructions" on this Letter of Transmittal should be completed.
 
   8. POUNDS STERLING OR IRISH POUNDS PAYMENT ELECTION. If the checks for the
purchase price are to be issued in pounds sterling or Irish pounds, please
check the appropriate box marked either "Pounds sterling Payment
<PAGE>
 
Election" or "Irish pounds Payment Election". If you do not check either of
such boxes or you check the "pounds sterling" box all Irish pound amounts
payable pursuant to the Offer will be converted by the US Depositary into US
dollars or pounds sterling (as appropriate) at the noon buying rate prevailing
in London for transfers in Irish pounds on the latest practicable business day
preceding the despatch of payment as certified by The Royal Bank of Scotland
plc.
 
   9. WAIVER OF CONDITIONS. ARCO Irish Holdings reserves the absolute right in
its sole discretion to waive any of the specified conditions of the Offer, in
whole or in part, in the case of any Aran ADSs accepted to the extent
permitted by applicable law and the rules of the City Code.
 
   10. 31% U.S. BACK-UP WITHHOLDING. In order to avoid "back-up withholding" of
U.S. Federal income tax on any cash payment received upon the surrender of
Aran ADSs pursuant to the Offer, an Aran ADS holder must, unless an exemption
applies, provide the US Depositary with his correct Taxpayer Identification
Number ("TIN") on Substitute Form W-9 on this Letter of Transmittal and
certify, under penalties of perjury, that such number is correct and that he
is not subject to back-up withholding. If the correct TIN is not provided a
$50 penalty may be imposed by the Internal Revenue Service and cash payments
made in exchange for the surrendered Aran ADSs may be subject to back-up
withholding of 31%.
 
   Back-up withholding is not an additional U.S. Federal income tax. Rather,
the U.S. Federal income tax liability of persons subject to back-up
withholding will be reduced by the amount of such tax withheld. If back-up
withholding results in an overpayment of taxes, a refund may be applied for
from the Internal Revenue Service.
 
   The TIN that is to be provided on the Substitute Form W-9 is that of the
registered holder(s) of the Aran ADSs or of the last transferee appearing on
the transfers attached to, or endorsed on, the Aran ADSs. The TIN for an
individual is his social security number. The box in Part 2 of the Substitute
Form W-9 may be checked, if the person surrendering the Aran ADSs has not been
issued a TIN and has applied for a TIN or intends to apply for a TIN in the
near future. If the box in Part 2 is checked, the person surrendering the Aran
ADSs must also complete the Certificate of Awaiting Taxpayer Identification
Number below. Notwithstanding that the box in Part 2 is checked (and the
Certificate of Awaiting Taxpayer Identification Number is completed), the US
Depositary will withhold 31% on any cash payment of the purchase price for the
Aran ADSs made prior to the time it is provided with a properly certified TIN.
 
   Exempt persons (including among others, corporations) are not subject to
back-up withholding. A foreign individual or foreign entity may qualify as an
exempt person by submitting a statement (on Form W-8), signed under penalties
of perjury, certifying such person's foreign status. Form W-8 can be obtained
from the US Depositary. An Aran ADS holder should consult his tax advisor as
to his qualification for an exemption from back-up withholding and the
procedure for obtaining such exemption.
 
   For additional guidance, see the enclosed Guidelines for Certification of
Taxpayer Identification Number on Substitute Form W-9.
 
   11. REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES. Questions and requests for
assistance or additional copies of the Offer Document, this Letter of
Transmittal, the Notice of Guaranteed Delivery and the guidelines for
certification of Taxpayer Identification Number on Substitute Form W-9 may be
directed to the US Depositary at the address and telephone number set forth
above or the Irish Receiving Agent or the UK Receiving Agent at the
appropriate address and telephone number set forth in the Offer Document.
 
   12. LOST, DESTROYED OR STOLEN CERTIFICATES. If any Aran ADR evidencing Aran
ADSs has been lost, destroyed or stolen, the holder thereof should promptly
notify the US Depositary by checking the box immediately preceding the special
payment/special delivery instructions and indicating the number of Aran ADSs
evidenced by such lost, destroyed or stolen Aran ADRs. The holder thereof will
then be instructed as to the steps that must be taken in order to replace such
Aran ADRs. This Letter of Transmittal and related documents cannot be
processed until the procedures for replacing lost, destroyed or stolen Aran
ADRs have been followed.
 
   13. HOLDERS OF ARAN SHARES NOT REPRESENTED BY ARAN ADSs. Holders of Aran
shares have been sent a Form of Acceptance with the Offer Document and may not
accept the Offer in respect of Aran shares pursuant to this Letter of
Transmittal except in so far as those shares are represented by Aran ADSs. If
any holder of Aran shares which are not represented by Aran ADSs needs to
obtain a copy of a Form of Acceptance, such holder should contact the Irish
Receiving Agent or the UK Receiving Agent at the appropriate address and
telephone number set forth in the Offer Document or the US Depositary. HOLDERS
OF ARAN ADSs MUST USE A LETTER OF TRANSMITTAL TO TENDER THEIR ARAN ADSs.
<PAGE>
 
             PAYER'S NAME: FIRST CHICAGO TRUST COMPANY OF NEW YORK
 
                    PART 1 - PLEASE PROVIDE YOUR TIN
                    IN THE BOX AT RIGHT AND CERTIFY
                    BY SIGNING AND DATING BELOW
 
                   -----------------------------------
 
                    CERTIFICATION - UNDER THE          Social Security Number
                    PENALTIES OF PERJURY, I CERTIFY    or Employer
                    THAT:                              Identification Number

                    1. The number shown on this form     --------------------
                       is my correct taxpayer             
                       identification number (or I     -----------------------
                       am waiting for a number to be                            
                       issued to me), and              
                                    

                                                               
                                                               
                    2. I am not subject to back-up
                       withholding because (a) I am
                       exempt from back-up
                       withholding or (b) I have not
                       been notified by the Internal
                       Revenue Service ("IRS") that
                       I am subject to back-up
                       withholding as a result of a
                       failure to report all
                       interest or dividends, or (c)
                       the IRS has notified me that
                       I am no longer subject to
                       back-up withholding.
  
   SUBSTITUTE      -----------------------------------
   Form W-9         Certification Instructions - you
   Department of    must cross out item 2 above if
   the Treasury     you have been notified by the
   Internal         IRS that you are currently
   Revenue          subject to back-up withholding
   Service          because of underreporting
                    interest or dividends on your
                    tax return.
                   
                    NAME ....................................
                                  (Please Print)
   Payer's          
   Request for      ADDRESS .................................
   Taxpayer       
   Identification   .........................................
   Number (TIN)                 (include Zip Code)                   Part 2  
                                                                [_]Awaiting TIN 
                    SIGNATURE ................. DATE .........


 YOU MUST COMPLETE THE FOLLOWING CERTIFICATION IF YOU CHECKED THE BOX IN PART 2
                            OF SUBSTITUTE FORM W-9

             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER
   I certify under penalties of perjury that a taxpayer identification
   number has not been issued to me, and either (a) I have mailed or
   delivered an application to receive a taxpayer identification
   number to the appropriate Internal Revenue Service Center or Social
   Security Administration Office or (b) I intend to mail or deliver
   an application in the near future. I understand that,
   notwithstanding that I have checked the box in Part 2 (and have
   completed this Certificate of Awaiting Taxpayer Identification
   Number), all reportable payments made to me prior to the time I
   provide the US Depositary with a properly certified taxpayer
   identification number will be subject to a 31% back-up withholding
   tax.

   Signature...............................   Date ........................ 

   NOTE: FAILURE TO COMPLETE AND RETURN THIS SUBSTITUTE FORM W-9 MAY
         RESULT IN BACK-UP WITHHOLDING OF 31% OF ANY CASH PAYMENT MADE
         TO YOU. PLEASE REVIEW THE ENCLOSED GUIDELINES FOR
         CERTIFICATION OF TAXPAYER IDENTIFICATION NUMBER ON SUBSTITUTE
         FORM W-9 FOR ADDITIONAL DETAILS
 
                      The US Depositary for the Offer is:
 
                         First Chicago Trust Company of
                                    New York
                      Call: (800) 659-6111 (Toll Free) or
                                 (201) 324 0137
 
   Suite 4680                                                Suite 4660
   14 Wall Street                                         P.O. Box 2559
   Eighth Floor                                   Jersey City, NJ 07303
   New York, NY 10005
 
                    The US Dealer Manager for the Offer is:
 
                                Rothschild Inc.
                          1251 Avenue of The Americas
                                   51st Floor
                               New York, NY 10020
                      (212) 403-3611 within New York City
           (800) 753-5151 ext. 3611 (Toll Free) outside New York City

<PAGE>

                                                                EXHIBIT 99(a)(3)

THIS DOCUMENT IS IMPORTANT AND REQUIRES YOUR IMMEDIATE ATTENTION. If you are in
any doubt about the action you should take, you are recommended to seek advice
from your own appropriately authorised independent financial adviser.
 
N M Rothschild & Sons Limited ("Rothschilds") is acting for Atlantic Richfield
Company ("ARCO") and ARCO Irish Holdings Inc. ("ARCO Irish Holdings") in
relation to the Offer and no one else, and will not be responsible to anyone
other than ARCO and ARCO Irish Holdings for providing the protection afforded
to customers of Rothschilds nor for providing advice in relation to the Offer.
Rothschilds is acting through Rothschild Inc. for the purpose of making the
Offer in the United States.
 
If you have sold or otherwise transferred all your shares in Aran Energy plc
("Aran"), please pass this document, all accompanying documents and (where
applicable) the accompanying reply-paid envelope as soon as possible to the
purchaser or transferee, or to the bank, stockbroker or other agent through
whom the sale or transfer was effected, for transmission to the purchaser or
transferee. HOWEVER, THIS FORM OF ACCEPTANCE SHOULD NOT BE DISTRIBUTED,
FORWARDED OR TRANSMITTED IN OR INTO AUSTRALIA, CANADA, OR JAPAN.
 
This Form should be read in conjunction with the accompanying offer document
dated 25 August 1995 from Rothschilds (the "Offer Document"). The definitions
used in the Offer Document also apply, where the context requires, in this
Form.
--------------------------------------------------------------------------------
 
                   FORM OF ACCEPTANCE, AUTHORITY AND ELECTION
 
                                   CASH OFFER
 
                                       BY
 
                         N M ROTHSCHILD & SONS LIMITED
 
                                  ON BEHALF OF
 
                            ARCO IRISH HOLDINGS INC.
 
                      TO ACQUIRE THE ENTIRE SHARE CAPITAL
 
                                       OF
 
                                ARAN ENERGY PLC
 
--------------------------------------------------------------------------------
 
                               ACTION TO BE TAKEN
 
 .  Please read pages 2 and 4 of this Form, where detailed instructions on how
   to complete this Form and accept the Offer in respect of your Aran shares
   are set out, and complete and sign page 3, in the presence of a witness (who
   should also sign where indicated).
 
                                    AND THEN
 
   return this Form, duly completed and signed, together with your share
   certificate(s) and/or other document(s) of title, either by hand or by post
   to AIB Bank, Registrars' & New Issue Department, Bankcentre, P.O. Box 954,
   Ballsbridge, Dublin 4 or The Royal Bank of Scotland plc, Registrar's
   Department, New Issues Section, P.O. Box 859, Consort House, East Street,
   Bedminster, Bristol BS99 1XZ or by hand only to The Royal Bank of Scotland
   plc, Registrar's Department, New Issues Section, 67 Lombard Street, London
   EC3P 3DL or, by post to First Chicago Trust Company of New York, Suite 4660,
   P.O. Box 2559, Jersey City, NJ 07303 or by hand or overnight courier to First
   Chicago Trust Company of New York, Suite 4680, 14 Wall Street, Eighth Floor,
   New York, NY 10005 AS SOON AS POSSIBLE, AND IN ANY EVENT SO AS TO BE RECEIVED
   BY NOT LATER THAN 3.00 P.M. (DUBLIN AND LONDON TIME), 10.00 A.M. (NEW YORK
   CITY TIME) ON 23 SEPTEMBER 1995. A REPLY-PAID ENVELOPE IS ENCLOSED FOR YOUR
   USE IF YOU HAVE A REGISTERED ADDRESS IN THE REPUBLIC OF IRELAND OR THE UNITED
   KINGDOM.
 
 .  If you are sending this document to First Chicago Trust Company of New York
   you should refer to the discussion of US back-up withholding requirements in
   paragraph 12 of Appendix 4 to the Offer Document.
 
 .  If your share certificate(s) and/or other document(s) of title is/are with
   your bank, stockbroker or other agent, you should complete and sign this
   Form and arrange for it to be lodged by such agent with the relevant
   document(s).
 
 .  If your share certificate(s) and/or other document(s) of title is/are not
   readily available, the Form should nevertheless be signed and returned as
   stated above and the share certificate(s) and/or other document(s) of title
   forwarded as soon as possible thereafter to AIB Bank, The Royal Bank of
   Scotland plc or, if appropriate, First Chicago Trust Company of New York, at
   any of the addresses given above.
 
 .  The provisions of Appendix 1 of the Offer Document are deemed to be
   incorporated in, and form part of, this Form and should be read in
   conjunction with this Form.
 
 .  If you hold Aran shares jointly with others, you must arrange for your co-
   holders to sign this Form.
 
IF YOU HAVE ANY QUESTIONS AS TO HOW TO COMPLETE THIS FORM, PLEASE TELEPHONE AIB
BANK IN DUBLIN ON 01 660 0311 (EXT. 12280), THE ROYAL BANK OF SCOTLAND PLC IN
BRISTOL ON 0117 9370666 OR FIRST CHICAGO TRUST COMPANY OF NEW YORK IN THE US ON
(800) 659 6111 (TOLL FREE) OR (201) 324 0137.
<PAGE>
 
                                     Page 2
 
                           How to complete this Form
THIS FORM MAY NOT BE USED TO ACCEPT THE OFFER IN RESPECT OF ARAN ADSs. Holders
of Aran ADSs wishing to accept the Offer in respect of such securities should
complete a Letter of Transmittal and any of the documents related thereto if
applicable. Copies of these documents may be obtained from AIB Bank, The Royal
Bank of Scotland plc or First Chicago Bank of New York at the appropriate
address on the front cover of this Form.
 
--------------------------------------------------------------------------------
 
          PLEASE FOLLOW THE INSTRUCTIONS BELOW WHEN COMPLETING PAGE 3.
 
 YOUR ACCEPTANCE SHOULD BE RECEIVED AS SOON AS POSSIBLE AND IN ANY EVENT BY NOT
 LATER THAN 3.00 P.M. (DUBLIN AND LONDON TIME), 10.00 A.M. (NEW YORK CITY TIME)
                             ON 23 SEPTEMBER 1995.
 
[1] TO ACCEPT THE OFFER FOR YOUR ARAN SHARES
 
    INSERT INTO BOX [1] THE       INCOMPLETE OR INACCURATE
    TOTAL NUMBER OF ARAN          ACCEPTANCES: If no
    SHARES FOR WHICH YOU WISH     number, or a number
    TO ACCEPT THE OFFER. YOU      greater than your entire              ICON   
    MUST ALSO SIGN BOX [2],       registered holding of              INDICATING
    IN THE PRESENCE OF A          Aran shares, is inserted            TO "SEE  
    WITNESS, WHICH WILL           in Box [1] and you sign            NEXT PAGE" 
    CONSTITUTE YOUR               Box [2], you will be
    ACCEPTANCE OF THE OFFER,      deemed to have accepted
    AND COMPLETE BOX [3].         the Offer in respect of,
    YOU SHOULD ALSO COMPLETE      and to have inserted in
    BOXES [4] AND/OR [5],         Box [1], the number of
    [6] OR [7] IF                 your entire registered
    APPROPRIATE.                  holding of Aran shares.
 
--------------------------------------------------------------------------------
 
[2] SIGNATURES
 
    YOU MUST SIGN                 applicable, a corporation
    BOX [2] REGARDLESS OF         may execute this Form as
    WHICH OTHER BOX(ES) YOU       a deed in any manner
    COMPLETE.                     permitted by the laws of
                                  the territory in which
    IN THE CASE OF JOINT          the corporation is
    HOLDERS ALL SUCH HOLDERS      incorporated for the
    MUST SIGN.                    execution of this Form as
                                  a deed.                               ICON   
    YOU MUST SIGN IN THE                                             INDICATING
    PRESENCE OF A WITNESS,        If this Form is not                 TO "SEE  
    WHO SHOULD ALSO SIGN          signed by the registered           NEXT PAGE"
    WHERE INDICATED, AND GIVE     holder(s), insert the       
    DETAILS OF HIS/HER NAME,      name(s) and capacity        
    ADDRESS AND OCCUPATION.       (e.g. executor(s)), of      
    THE WITNESS MUST NOT BE       the person(s) signing       
    ANOTHER JOINT HOLDER AND      this Form. You should       
    MUST BE OVER EIGHTEEN.        also deliver evidence of   
                                  your authority in          
    A corporation must            accordance with the notes  
    execute under seal, the       on page 4 of this Form.     
    seal being affixed and        
    witnessed in accordance       This Form shall take       
    with its Articles of          effect as a Deed executed  
    Association or other          by you and by any joint   
    regulations.                  holder(s).                 
    Alternatively, where         
 
--------------------------------------------------------------------------------
                                                                       
[3] FULL NAME(S) AND ADDRESS                                          
                                                                    
    Complete Box [3] with         CAPITALS, and provide a             
    the full name and address     daytime telephone number              ICON   
    of the sole or first-         whereupon you may be               INDICATING 
    named registered holder       contacted in the event of           TO "SEE  
    together with the names       any query.                         NEXT PAGE" 
    of all other joint
    holders (if any) in BLOCK
 
--------------------------------------------------------------------------------
                                                                        
[4] ALTERNATIVE ADDRESS                                               
                                                                    
    If you want the               your bank manager or                  ICON   
    consideration and other       stockbroker), you should           INDICATING
    documents to be sent to       also complete Box [4] in            TO "SEE  
    someone other than the        BLOCK CAPITALS with an             NEXT PAGE" 
    first-named registered        address outside
    holder at the address set     Australia, Canada or
    out in Box [3] (e.g.          Japan.
 
--------------------------------------------------------------------------------
                                                                        
[5] IRISH POUNDS PAYMENT ELECTION                                     
                                                                    
    Accepting Aran                put a "X" in Box [5];               
    shareholders with             otherwise you will                    ICON   
    registered addresses in       receive payment in pounds          INDICATING
    the UK who wish to            sterling (unless you                TO "SEE  
    receive payment of all        elect to receive US                NEXT PAGE" 
    (but not part) of the         dollars -- see Box [7]).
    consideration to be paid
    in Irish pounds,
 
  NOTE: SEE PARAGRAPH 16 ON PAGE 14 OF OFFER DOCUMENT FOR FURTHER INFORMATION
  ON THE CURRENCY ELECTIONS.
 
--------------------------------------------------------------------------------
                                                                        
[6] POUNDS STERLING PAYMENT ELECTION                                  
                                                                    
    Accepting Aran                conversion of the
    shareholders with             consideration payable to
    registered addresses          you (based on the Irish
    outside the UK who wish       pounds Offer price) into
    to receive payment of all     pounds sterling at the
    (but not part) of the         noon buying rate                      ICON   
    consideration to be paid      prevailing in London for           INDICATING
    in pounds sterling, put a     transfers in Irish pounds           TO "SEE  
    "X" in Box [6];               on the latest practicable          NEXT PAGE" 
    otherwise you will            business day preceding
    receive payment in Irish      the date of despatch of
    pounds (unless you elect      payment as certified by
    to receive US dollars --      The Royal Bank of
    see Box [7]). If you put      Scotland plc. All costs
    a "X" in Box [6], ARCO        of such conversion will
    Irish Holdings will           be paid by ARCO Irish
    arrange for the               Holdings.
 
  NOTE: SEE PARAGRAPH 16 ON PAGE 14 OF OFFER DOCUMENT FOR FURTHER INFORMATION
  ON THE CURRENCY ELECTIONS.
 
--------------------------------------------------------------------------------
 
[7] US DOLLARS PAYMENT ELECTION
 
    Any accepting Aran            consideration payable to
    shareholders who wish to      you (based on the Irish
    receive payment of all        pounds Offer price) into
    (but not part) of the         US dollars at the noon              
    consideration to be paid      buying rate prevailing in           
    in US dollars, put a "X"      London for transfers in             
    in Box [7]; otherwise         Irish pounds on the                   ICON   
    (unless you specify           latest practicable                 INDICATING
    differently in Box [5]        business day preceding              TO "SEE  
    or Box [6]) you will          the date of despatch of            NEXT PAGE" 
    automatically receive         payment as certified by
    payment in Irish pounds       The Royal Bank of
    or, if you have a             Scotland plc. All costs
    registered address in the     of such conversion will
    UK, pounds sterling. If       be paid by ARCO Irish
    you put a "X" in              Holdings.
    Box [7], ARCO Irish
    Holdings will arrange for
    the conversion of the
 
  NOTE: SEE PARAGRAPH 16 ON PAGE 14 OF OFFER DOCUMENT FOR FURTHER INFORMATION
  ON THE CURRENCY ELECTIONS.
 
--------------------------------------------------------------------------------
<PAGE>
 
                                    Page 3
--------------------------------------------------------------------------------
Please complete as explained on pages 2 and 4                        For office 
--------------------------------------------------------------------  use only
                                                                     -----------
[1] To accept the Offer                                    Box [1]     H
 
    Complete Box [1] and Box [3] and
    sign Box [2] below in the presence of
    a witness who should sign and give       No. of Aran shares___ 
    details of his/her name, address and
    occupation where indicated.                                      -----------
                                                                       C
  Please also complete Boxes [4] and/or [5], [6], or [7] if          
  appropriate. PLEASE READ CAREFULLY THE INSTRUCTIONS OPPOSITE BOXES
  [5], [6], AND [7] ON PAGE 2 REGARDING THE CURRENCY IN WHICH
  YOU WILL RECEIVE YOUR CONSIDERATION.
 
--------------------------------------------------------------------------------
 
[2] Sign here to accept the Offer                          Box [2]     Q
 
         SIGNED AS A DEED AND DELIVERED BY/EXECUTED AS A DEED BY:  
                                                                       
         1. Signature of holder_____   3. Signature of holder ____     
         in the presence of:           in the presence of:             
         (Witness) name ____________   (Witness) name ____________   -----------
         Address ___________________   Address ___________________     
         Occupation ________________   Occupation ________________     
         Signature of witness ______   Signature of witness ______     
                                                                       
         2. Signature of holder ____   4. Signature of holder ____     
         in the presence of:           in the presence of:             
         (Witness) name ____________   (Witness) name ____________     
         Address ___________________   Address ___________________     
         Occupation ________________   Occupation ________________     
         Signature of witness ______   Signature of witness ______     
         ---------------------------------------------------------     
                                       Director __________________     
         For use by a corporation      Signature _________________     
         Executed as a Deed by _____   Director/Secretary ________     
         ___________________________   Signature _________________     
         (name of corporation)                                          

--------------------------------------------------------------------------------
 
[3] Full name(s) and address                               Box [3]
 
                First-named registered       Joint registered holders
                       holder
 
 
              1. Forename(s)               2. Forename(s)
              ---------------------------  ---------------------------
              (Mr, Mrs, Ms, Miss or        (Mr, Mrs, Ms, Miss or
              Title)                       Title)
              
              Surname                      Surname
              ---------------------------  ---------------------------
              
              Address                      3. Forename(s)
              ---------------------------  ---------------------------
              ---------------------------  (Mr, Mrs, Ms, Miss or
              ---------------------------  Title)
              
              Postcode                     Surname
              ---------------------------  ---------------------------

                                           4. Forename(s)
                                           ---------------------------
                                           (Mr, Mrs, Ms, Miss or
                                           Title)

                                           Surname
                                           ---------------------------
 
             Please give a daytime telephone number where you may be
             contacted in the event of a query. Tel.:
 
--------------------------------------------------------------------------------
 
[4] Address to which consideration and                      Box [4] 
    other document(s) are to be sent if                                   
    not your own (to be completed in block
    capitals)
                                              Name _____________________
    IRISH REGISTERED SHAREHOLDERS WHO WISH    Address __________________
    TO RECEIVE PAYMENT IN IRISH POUNDS        __________________________
    SHOULD NOT COMPLETE ANY OF BOXES          Postcode _________________
     [5], [6] OR [7]
 
--------------------------------------------------------------------------------
 
[5] If you have a registered address in the UK and wish to receive payment in
    Irish pounds, put a "X" in Box [5]. Unless you have marked this Box or
    Box [7], you will receive pounds sterling.
                                                           Box 5 [_]
 
--------------------------------------------------------------------------------
 
[6] If you have a registered address outside the UK and wish to receive payment
    in pounds sterling, put a "X" in Box [6]. Unless you have marked this Box
    or Box [7], you will receive Irish pounds.
                                                           Box 6 [_]
 
--------------------------------------------------------------------------------
 
[7] If you wish to receive payment in US dollars, put a "X" in Box [7]

                                                           Box 7 [_]
 
--------------------------------------------------------------------------------
                     FOR USE BY REGISTRARS/STOCK EXCHANGE


-------------------------------------------------------------------------------
<PAGE>
 
                                    Page 4

        FURTHER NOTES REGARDING THE COMPLETION AND LODGING OF THIS FORM
 
In order to avoid delay and inconvenience to yourself, the following points
may assist you.
 
1.  IF A HOLDER IS AWAY FROM HOME (E.G. ABROAD OR ON HOLIDAY)

    Send this Form by the quickest means (e.g. air mail) to the holder for
    execution (but not into Australia, Canada or Japan) or, if he has executed a
    power of attorney, have this Form signed by the attorney in the presence of
    a witness. In the latter case, the original power of attorney (or a copy
    thereof duly certificated in accordance with the Powers of Attorney Act 1971
    of the United Kingdom) must be lodged with this Form for noting. No other
    signatures are acceptable.
 
2.  IF YOU HAVE SOLD OR TRANSFERRED ALL YOUR ARAN SHARES

    You should at once send this Form, together with the accompanying Offer
    Document and (where provided) the reply-paid envelope, as soon as possible
    to the purchaser or transferee, or, to the bank, stockbroker or other agent
    through whom the sale or transfer was effected for onward transmission to
    the purchaser or transferee. However, this Form of Acceptance should not be
    distributed, forwarded or transmitted to Australia, Canada or Japan.
 
3.  IF THE SOLE HOLDER HAS DIED

    If the Grant of Probate or Letters of Administration or equivalent
    documentation has/have been registered with Aran (or its registrars), this
    Form must be signed by the personal representative(s) of the deceased or
    equivalent person and lodged with AIB Bank, The Royal Bank of Scotland plc
    or First Chicago Trust Company of New York (as appropriate), at the
    appropriate address given on page 1 of this Form. If the Grant of Probate or
    Letters of Administration or equivalent document has/have not been
    registered with Aran (or its registrars), the personal representative(s) or
    the prospective personal representative(s) should sign this Form in the
    presence of a witness and forward it to AIB Bank, The Royal Bank of Scotland
    plc or First Chicago Trust Company of New York (as appropriate), with the
    share certificate(s) and/or other document(s) of title and a sealed copy of
    the Grant of Probate or Letters of Administration or equivalent
    documentation must be lodged as soon as possible thereafter and in any case
    before the cash remittances due under the Offer can be forwarded to the
    personal representative(s).
 
4.  IF ONE OF THE HOLDERS OF A JOINT ACCOUNT HAS DIED

    This Form must be signed by all the surviving holders, each in the presence
    of a witness, and lodged with AIB Bank, The Royal Bank of Scotland plc or
    First Chicago Trust Company of New York (as appropriate), at the appropriate
    address given on page 1 of this Form with the share certificate(s) and/or
    other document(s) of title, accompanied by the death certificate, Grant of
    Probate or Letters of Administration or equivalent documentation in respect
    of the deceased holder.
 
5.  IF YOU DO NOT HAVE YOUR SHARE CERTIFICATE(S) AND/OR OTHER DOCUMENT(S) OF
    TITLE

    If your share certificate and/or other document(s) of title is/are held by
    your bank or some other agent, complete this Form and, if the share
    certificate(s) is/are readily obtainable, deliver this completed Form to
    your agent for lodging with AIB Bank, The Royal Bank of Scotland plc or
    First Chicago Trust Company of New York (as appropriate), at the appropriate
    address given on page 1 of this Form, accompanied by the share
    certificate(s) and/or other document(s) of title.

    If the share certificate(s) and/or other document(s) of title is/are not
    readily available, you should complete this Form and lodge it together with
    such document(s) of title as is/are available and a letter stating that
    all/the balance of such document(s) of title will follow as soon as possible
    thereafter or alternatively that you have lost one or more of your share
    certificate(s) and, if applicable, arrange for the share certificate(s)
    and/or other document(s) of title to be forwarded as soon as possible
    thereafter.

    If the share certificate(s) and/or other document(s) of title has/have been
    lost, you should complete this Form and lodge it, together with any
    certificate(s) available, with AIB Bank, The Royal Bank of Scotland plc or
    First Chicago Trust Company of New York (as appropriate), at the appropriate
    address given on page 1 of this Form. At the same time you should write to
    the registrars of Aran who are Bank of Ireland, Registrars' Department, P.O.
    Box 4044, Hume House, Ballsbridge, Dublin 4, Ireland, advising them of the
    loss and asking for a letter of indemnity which must be completed in
    accordance with the instructions given. When completed, the letter of
    indemnity must be lodged with AIB Bank, The Royal Bank of Scotland plc or
    First Chicago Trust Company of New York (as appropriate), at the address
    given on page 1 of this Form and to which you sent your Form of Acceptance.
 
6.  IF THE FORM HAS BEEN SIGNED UNDER POWER OF ATTORNEY

    The completed Form together with the share certificate(s) should be lodged
    with AIB Bank, The Royal Bank of Scotland plc or First Chicago Trust Company
    of New York (as appropriate), at the appropriate address given on page 1 of
    this Form, accompanied by the original power of attorney (or a copy thereof
    duly certified in accordance with the Powers of Attorney Act 1971 of the
    United Kingdom) for noting.
 
7.  IF YOUR FULL NAME OR OTHER PARTICULARS ARE SHOWN INCORRECTLY ON THE SHARE
    CERTIFICATE(S), FOR EXAMPLE

    (a)  Name on the certificate.....................................John Burk
         Correct name................................................John Burke

         Complete this Form with the correct name and lodge it, accompanied by a
         letter from your bank, stockbroker or solicitor confirming that the
         person described on the certificate(s) and the person who signed this
         Form are one and the same.

    (b)  Incorrect address

         Write the correct address on this Form.

    (c)  Change of name

      If you have changed your name, lodge your marriage certificate or the
    deed poll with this Form for noting. Cash remittances due to you under the
    Offer cannot be sent until all relevant documents have been properly
    completed and lodged, either by post or by hand to AIB Bank, Registrars' &
    New Issue Department, Bankcentre, P.O. Box 954, Ballsbridge, Dublin 4 or The
    Royal Bank of Scotland plc, Registrar's Department, New Issues Section, P.O.
    Box 859, Consort House, East Street, Bedminster, Bristol BS99 1XZ or by hand
    only to The Royal Bank of Scotland plc, Registrar's Department, New Issues
    Section, 67 Lombard Street, London, EC3P 3DL or, if more convenient, by post
    to First Chicago Trust Company of New York, Suite 4660, P.O. Box 2559,
    Jersey City, NJ 07303 or by hand or overnight courier to First Chicago Trust
    Company of New York, Suite 4680, 14 Wall Street, Eighth Floor, New York, NY
    10005. Subject to the provisions of the City Code, ARCO Irish Holdings and
    Rothschilds reserve the right to treat as valid, in whole or in part,
    acceptances of the Offer which are not entirely in order or which are not
    accompanied by the relevant share certificate(s) and/or other document(s) of
    title.
 
                   Printed by RR Donnelley Financial, 13887

<PAGE>

                                                                EXHIBIT 99(a)(4)
 
THIS DOCUMENT IS IMPORTANT AND REQUIRES YOUR IMMEDIATE ATTENTION. If you are
in any doubt about any action you should take, you are recommended to seek
advice from your own appropriately authorized independent financial adviser.
 
N M Rothschild & Sons Limited ("Rothschilds") is acting for Atlantic Richfield
Company ("ARCO") and ARCO Irish Holdings Inc. ("ARCO Irish Holdings") in
relation to the Offer and no one else, and will not be responsible to anyone
other than ARCO and ARCO Irish Holdings for providing the protection afforded
to customers of Rothschilds nor for providing advice in relation to the Offer.
Rothschilds is acting through Rothschild Inc. for the purpose of making the
Offer in the United States.
 
If you have sold or otherwise transferred all your American Depositary Shares
("Aran ADSs") of Aran Energy plc, please pass this document and all
accompanying documents as soon as possible to the purchaser or transferee, or
to the bank, stockbroker or other agent through whom the sale or transfer was
effected for transmission to the purchaser or transferee. HOWEVER, SUCH
DOCUMENTS SHOULD NOT BE DISTRIBUTED, FORWARDED OR TRANSMITTED IN OR INTO
AUSTRALIA, CANADA OR JAPAN.
 
This Notice should be read in conjunction with the accompanying offer document
dated August 25th, 1995 (the "Offer Document"). The definitions used in the
Offer Document also apply, where the context requires, in this Notice.
 
-------------------------------------------------------------------------------
 
                         NOTICE OF GUARANTEED DELIVERY
 
                                      FOR
 
            ACCEPTANCE OF THE OFFER FOR AMERICAN DEPOSITARY SHARES
 
 
                                      OF
 
                                ARAN ENERGY PLC
 
             PURSUANT TO THE OFFER DOCUMENT DATED AUGUST 25, 1995
 
                                      BY
 
                         N M ROTHSCHILD & SONS LIMITED
 
                                 ON BEHALF OF
 
                           ARCO IRISH HOLDINGS INC.
 
                      (A WHOLLY OWNED SUBSIDIARY OF ARCO)
 
-------------------------------------------------------------------------------
 
As set forth in "Acceptance procedures for holders of Aran ADSs" in Part B of
Appendix 1 to the Offer Document, this form or one substantially equivalent
hereto must be used for acceptance of the Offer in respect of Aran ADSs, if
Aran American Depositary Receipts evidencing Aran ADSs ("Aran ADRs") are not
immediately available or the procedures for book-entry transfer cannot be
completed on a timely basis or if time will not permit all required documents
to reach the US Depositary prior to the expiry of the Offer. Such form may be
delivered by hand or transmitted by facsimile transmission or mailed to the US
Depositary and must include a signature guarantee by an Eligible Institution
in the form set out herein. See "Acceptance procedures for holders of Aran
ADSs--Guaranteed delivery procedures" in Part B of Appendix 1 to the Offer
Document.
 
-------------------------------------------------------------------------------
 
                  TO: FIRST CHICAGO TRUST COMPANY OF NEW YORK
                                 US DEPOSITARY
 
By Mail:                    By Facsimile Transmission      By Hand or Overnight
                        (for Eligible Institutions only):         Delivery:
     
     Suite 4660             Fax: (201) 222-4720 or 4721          Suite 4680   
    P.O. Box 2559          Confirm Receipt of Notice of        14 Wall Street 
Jersey City, NJ 07303           Guaranteed Delivery              Eighth Floor 
                                   by Telephone:              New York, NY 10005
                                  (201) 222-4707       
                                                           
                               For Information call:       
                                                           
                            (800) 659-6111 (Toll Free)     
                                        or                 
                                  (201) 324 0137            
                        
 
DELIVERY OF THIS INSTRUMENT TO AN ADDRESS, OR TRANSMISSION OF INSTRUCTIONS VIA
A FACSIMILE OR TELEX NUMBER, OTHER THAN AS SET FORTH ABOVE, DOES NOT
CONSTITUTE A VALID DELIVERY.
<PAGE>
 
This form is not to be used to guarantee signatures. If a signature on a
Letter of Transmittal is required to be guaranteed by an Eligible Institution
under the instruction thereto, such signature guarantee must appear in the
applicable space provided in the signature box on the Letter of Transmittal.
 
ACCEPTANCE OF THE OFFER IN RESPECT OF ARAN SHARES (EXCEPT INSOFAR AS THEY ARE
REPRESENTED BY ARAN ADSs) MAY NOT BE MADE WITH THIS FORM AND PURSUANT TO THE
GUARANTEED DELIVERY PROCEDURES. IF YOU HOLD ARAN SHARES THAT ARE NOT
REPRESENTED BY ARAN ADSs, YOU CAN OBTAIN A FORM OF ACCEPTANCE FOR ACCEPTING
THE OFFER IN RESPECT OF THOSE ARAN SHARES FROM THE IRISH RECEIVING AGENT, THE
UK RECEIVING AGENT OR THE US DEPOSITARY. SEE INSTRUCTION 13 OF THE LETTER OF
TRANSMITTAL.
 
Ladies and Gentlemen:
 
The undersigned hereby accepts the Offer in respect of Aran ADSs upon the
terms and subject to the conditions set forth below pursuant to the guaranteed
delivery procedures set out in "Acceptance procedures for holders of Aran
ADSs--Guaranteed delivery procedures" in Part B of Appendix 1 to the Offer
Document.
 
THE UNDERSIGNED UNDERSTANDS THAT THE ACCEPTANCE OF THE OFFER IN RESPECT OF
ARAN ADSs PURSUANT TO THE GUARANTEED DELIVERY PROCEDURES WILL NOT BE TREATED
AS A VALID ACCEPTANCE FOR THE PURPOSE OF SATISFYING THE ACCEPTANCE CONDITION.
SEE "ACCEPTANCE PROCEDURES FOR HOLDERS OF ARAN ADSs--GUARANTEED DELIVERY
PROCEDURES" IN PART B OF APPENDIX 1 TO THE OFFER DOCUMENT. TO BE COUNTED
TOWARDS SATISFACTION OF THIS CONDITION, THE ARAN ADRs EVIDENCING SUCH ARAN
ADSs MUST BE RECEIVED BY THE US DEPOSITARY OR, IF APPLICABLE, TIMELY
CONFIRMATION OF A BOOK-ENTRY TRANSFER OF SUCH ARAN ADSs INTO THE US
DEPOSITARY'S ACCOUNT AT A BOOK-ENTRY TRANSFER FACILITY PURSUANT TO THE
PROCEDURES SET OUT IN "ACCEPTANCE PROCEDURES FOR HOLDERS OF ARAN ADSs--BOOK
ENTRY TRANSFER FACILITIES" IN PART B OF APPENDIX 1 TO THE OFFER DOCUMENT MUST
BE RECEIVED BY THE US DEPOSITARY, TOGETHER WITH A DULY EXECUTED LETTER OF
TRANSMITTAL (OR FACSIMILE THEREOF) WITH ANY REQUIRED SIGNATURE GUARANTEES AND
ANY OTHER REQUIRED DOCUMENTS.
 
Number of Aran ADSs: ________________    Name of Record Holder(s): ___________
 
Aran ADR No.(s) (if available): _____    _____________________________________
 
_____________________________________    _____________________________________
                                                (Please type or print)
 
_____________________________________    Address _____________________________
 
If Aran ADSs will be tendered by         _____________________________________
book-entry
transfer check one box:
 
                                         Area Code and Tel. No.: _____________
[_]The Depositary Trust Company
                                         Signature(s): _______________________
[_]Midwest Securities Trust Company
                                         _____________________________________
[_]Philadelphia Depositary Trust
   Company
                                         _____________________________________
 
Account Number: _____________________    Dated: ______________________________
<PAGE>
 
                                   GUARANTEE
                   (NOT TO BE USED FOR SIGNATURE GUARANTEES)
 
  The undersigned, a participant in the Securities Transfer Agents Medallion
Program, the New York Stock Exchange Medallion Program or the Stock Exchanges
Medallion Program, hereby guarantees that the undersigned will deliver to the
US Depositary either the Aran ADRs representing the Aran ADSs with respect to
which the Offer is being accepted hereby, in proper form for transfer, or
confirmation of the book-entry transfer of such Aran ADSs into the US
Depositary's account at The Depositary Trust Company, the Midwest Securities
Trust Company or the Philadelphia Depositary Trust Company, in any such case
together with a properly completed and duly executed Letter of Transmittal (or
manually signed facsimile thereof), with any required signature guarantees and
any other required documents, all within three NASDAQ trading days after the
date hereof.
 
  The Eligible Institution that completes this form must communicate the
guarantee to the US Depositary and must deliver the Letter of Transmittal and
Aran ADRs to the US Depositary within the time periods shown herein. Failure
to do so could result in a financial loss to such Eligible Institution.
 
Number of Firm, Agent or Trustee: ___    _____________________________________
                                                (Authorized Signature)
 
_____________________________________    Name: _______________________________
                                                (Please type or print)
 
Address: ____________________________    Title: ______________________________
                           (Zip Code)
 
Area Code and Tel. No.: _____________    Dated: ______________________________
 
NOTE: DO NOT SEND ARAN ADRs WITH THIS FORM; ARAN ADRs SHOULD BE SENT WITH YOUR
      LETTER OF TRANSMITTAL

<PAGE>

                                                                EXHIBIT 99(a)(5)

   This document should not be forward or transmitted in or into Australia,
                               Canada or Japan.
 
ROTHSCHILD INC.
 
                   OFFER FOR ALL OUTSTANDING ORDINARY SHARES

                        AND AMERICAN DEPOSITARY SHARES

                                      OF

                                ARAN ENERGY PLC

                                      BY

                         N M ROTHSCHILD & SONS LIMITED

                                 ON BEHALF OF

                           ARCO IRISH HOLDINGS INC.

                      (A WHOLLY OWNED SUBSIDIARY OF ARCO)
 
 THE OFFER IS OPEN FOR ACCEPTANCE UNTIL 3:00 P.M. (DUBLIN AND LONDON TIME),
 10:00 A.M. (NEW YORK CITY TIME), ON SEPTEMBER 23, 1995 (THE "INITIAL
 PERIOD"), UNLESS EXTENDED (IN ACCORDANCE WITH THE TERMS THEREOF). AT THE
 CONCLUSION OF THE INITIAL PERIOD OR ON OR BEFORE THE CONCLUSION OF ANY
 EXTENSION THEREOF AND ON THE SATISFACTION OR, WHERE PERMITTED, WAIVER OF THE
 CONDITION(S) TO THE OFFER, THE PURCHASE OF ALL ARAN SECURITIES IN RESPECT OF
 WHICH THE OFFER HAS BEEN VALIDLY ACCEPTED AND NOT WITHDRAWN WILL TAKE PLACE,
 AND THE OFFER WILL BE EXTENDED FOR A SUBSEQUENT PERIOD OF AT LEAST FOURTEEN
 CALENDAR DAYS. PRIOR TO THE OFFER BECOMING OR OTHERWISE BEING DECLARED
 UNCONDITIONAL IN ALL RESPECTS, ACCEPTING ARAN SECURITYHOLDERS WILL HAVE THE
 RIGHT TO WITHDRAW THEIR ACCEPTANCES IN RESPECT THEREOF. HOWEVER, IN THE
 EVENT OF THE OFFER BECOMING OR BEING DECLARED UNCONDITIONAL IN ALL RESPECTS,
 NO RIGHTS OF WITHDRAWAL WILL BE AVAILABLE TO ACCEPTING ARAN SECURITYHOLDERS
 IN THE SUBSEQUENT PERIOD DURING WHICH THE OFFER REMAINS OPEN FOR ACCEPTANCE.
 
                                                                August 25, 1995
 
To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:
 
   Rothschild Inc. has been appointed by ARCO Irish Holdings Inc. ("ARCO Irish
Holdings") to act as dealer manager in the United States (the "US Dealer
Manager") in connection with an offer by N M Rothschild & Sons Limited, acting
in the United States through Rothschild Inc., and on behalf of ARCO Irish
Holdings, to purchase, upon the terms and subject to the conditions set forth
in the offer document dated August 25, 1995 (the "Offer Document") and the
accompanying Acceptance Forms (collectively, the "Offer"), all outstanding
ordinary shares of IR20p each ("Aran shares") of Aran Energy plc ("Aran") for
IR60p in cash, including all Aran shares represented by Aran American
Depositary Shares ("Aran ADSs"), each representing thirty Aran shares and
evidenced by Aran American Depositary Receipts ("Aran ADRs"), for
IR(Pounds)18.00 in cash. The Offer will extend to any Aran shares and Aran
ADSs unconditionally allotted or issued fully paid prior to the date on which
the Offer becomes or is declared unconditional (or such later date or dates as
ARCO Irish Holdings may decide) pursuant to the exercise of options granted
under Aran share option scheme(s) (as discussed in the Offer Document).
<PAGE>

2

  For your information and for forwarding to those of your clients for whom
you hold Aran ADSs registered in your name or in the name of your nominee, we
are enclosing the following documents:
 
   1.  The Offer Document;
 
   2.  A printed form of letter that may be sent to your clients for whose
       account you hold Aran ADSs registered in your name or in the name of
       a nominee, with space provided for obtaining such clients'
       instructions with regard to the Offer;
 
   3.  The Letter of Transmittal to be used by holders of Aran ADSs to
       accept the Offer;
 
   4.  The Notice of Guaranteed Delivery;
 
   5.  Guidelines for Certification of Taxpayer Identification Number on
       Substitute Form W-9; and
 
   6.  The return envelope addressed to the US Depositary.
 
   THE OFFER CANNOT BE ACCEPTED IN RESPECT OF ARAN SHARES (OTHER THAN ARAN
SHARES REPRESENTED BY ARAN ADSs) BY MEANS OF A LETTER OF TRANSMITTAL. A FORM
OF ACCEPTANCE FOR ACCEPTING THE OFFER IN RESPECT OF ARAN SHARES (OTHER THAN
ARAN SHARES REPRESENTED BY ARAN ADSs) CAN BE OBTAINED FROM THE US DEPOSITARY,
THE IRISH RECEIVING AGENT OR THE UK RECEIVING AGENT (AS EACH SUCH TERM IS
DEFINED IN THE OFFER DOCUMENT).
 
   In all cases, payment for Aran ADSs purchased pursuant to the Offer will be
made only after timely receipt by the US Depositary of Aran ADRs evidencing
such Aran ADSs or a confirmation of book-entry transfer, together with the
Letter of Transmittal (or a facsimile copy thereof) properly completed and
duly executed, and any other documents required by the Letter of Transmittal.
 
   ARCO Irish Holdings will not pay any fees or commissions to any broker,
dealer, or other person (other than N M Rothschild & Sons Limited, Hoare
Govett Corporate Finance Limited, Riada Corporate Finance Limited, the US
Dealer Manager, the US Depositary, the Irish Receiving Agent and the UK
Receiving Agent as described in the Offer Document) in connection with the
solicitation of acceptances of the Offer with respect to Aran ADSs. You will,
however, be reimbursed for customary mailing and handling expenses incurred by
you in forwarding the enclosed materials to your client.
 
   Additional copies of the enclosed materials may be obtained from the US
Depositary, the Irish Receiving Agent or the UK Receiving Agent at their
respective addresses and telephone numbers set forth in the Offer Document.
 
   Terms defined in the Offer Document shall have the same meanings in this
letter.
 
                               Very truly yours,
 
                                Rothschild Inc.
                          1251 Avenue of the Americas
                                  51st Floor
                              New York, NY 10020
                      (212) 403-3611 within New York City
          (800) 753-5151 ext. 3611 (Toll Free) outside New York City
 
 NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU
 OR ANY OTHER PERSON THE AGENT OF N M ROTHSCHILD & SONS LIMITED, ARCO IRISH
 HOLDINGS INC., ARCO, THE US DEPOSITARY, THE US DEALER MANAGER, THE IRISH
 RECEIVING AGENT OR THE UK RECEIVING AGENT OR AUTHORIZE YOU OR ANY OTHER
 PERSON TO GIVE ANY INFORMATION OR MAKE ANY REPRESENTATION ON BEHALF OF ANY
 OF THEM WITH RESPECT TO THE OFFER NOT CONTAINED IN THE OFFER DOCUMENT OR THE
 LETTER OF TRANSMITTAL.
 

<PAGE>

                                                                EXHIBIT 99(a)(6)
 
  This document should not be forwarded or transmitted in or into Australia,
                               Canada or Japan.
 
ROTHSCHILD INC.
 
                   OFFER FOR ALL OUTSTANDING ORDINARY SHARES

                        AND AMERICAN DEPOSITARY SHARES

                                      OF

                                ARAN ENERGY PLC

                                      BY

                         N M ROTHSCHILD & SONS LIMITED

                                 ON BEHALF OF

                           ARCO IRISH HOLDINGS INC.

                      (A WHOLLY OWNED SUBSIDIARY OF ARCO)
 
 THE OFFER IS OPEN FOR ACCEPTANCE UNTIL 3:00 P.M. (DUBLIN AND LONDON TIME),
 10:00 A.M. (NEW YORK CITY TIME), ON SEPTEMBER 23, 1995 (THE "INITIAL
 PERIOD"), UNLESS EXTENDED (IN ACCORDANCE WITH THE TERMS THEREOF). AT THE
 CONCLUSION OF THE INITIAL PERIOD OR ON OR BEFORE THE CONCLUSION OF ANY
 EXTENSION THEREOF AND ON THE SATISFACTION OR, WHERE PERMITTED, WAIVER OF THE
 CONDITION(S) TO THE OFFER, THE PURCHASE OF ALL ARAN SECURITIES IN RESPECT OF
 WHICH THE OFFER HAS BEEN VALIDLY ACCEPTED AND NOT WITHDRAWN WILL TAKE PLACE,
 AND THE OFFER WILL BE EXTENDED FOR A SUBSEQUENT PERIOD OF AT LEAST FOURTEEN
 CALENDAR DAYS. PRIOR TO THE OFFER BECOMING OR OTHERWISE BEING DECLARED
 UNCONDITIONAL IN ALL RESPECTS, ACCEPTING ARAN SECURITYHOLDERS WILL HAVE THE
 RIGHT TO WITHDRAW THEIR ACCEPTANCES IN RESPECT THEREOF. HOWEVER, IN THE
 EVENT OF THE OFFER BECOMING OR BEING DECLARED UNCONDITIONAL IN ALL RESPECTS,
 NO RIGHTS OF WITHDRAWAL WILL BE AVAILABLE TO ACCEPTING ARAN SECURITYHOLDERS
 IN THE SUBSEQUENT PERIOD DURING WHICH THE OFFER REMAINS OPEN FOR ACCEPTANCE.
 
                                                                August 25, 1995
 
To holders of Aran shares (as defined below):
 
   Rothschild Inc. has been appointed by ARCO Irish Holdings Inc. ("ARCO Irish
Holdings") to act as dealer manager in the United States (the "US Dealer
Manager") in connection with an offer by N M Rothschild & Sons Limited, acting
in United States through Rothschild Inc., and on behalf of ARCO Irish
Holdings, to purchase, upon the terms and subject to the conditions set forth
in the offer document dated August 25, 1995 (the "Offer Document") and the
accompanying Acceptance Forms (collectively, the "Offer"), all outstanding
ordinary shares of IR20p each ("Aran shares") of Aran Energy plc ("Aran") for
IR60p in cash, including all Aran shares represented by Aran American
Depositary Shares ("Aran ADSs"), each representing thirty Aran shares and
evidenced by Aran American Depositary Receipts ("Aran ADRs"), for
IR(Pounds)18.00 in cash. The Offer will extend to any Aran shares and Aran
ADSs unconditionally allotted or issued fully paid prior to the date on which
the Offer becomes or is declared unconditional (or such later date or dates as
ARCO Irish Holdings may decide) pursuant to the exercise of options granted
under Aran share option scheme(s) (as discussed in the Offer Document).
<PAGE>

2

   We are enclosing the following documents:
 
   1.  The Offer Document;
 
   2.  The Form of Acceptance to be used by holders of Aran shares accepting
       the Offer;
 
   3.  Guidelines for Certification of Taxpayer Identification Number on
       Substitute Form W-9; and
 
   4.  The return envelope addressed to the US Depositary.
 
 .    THE OFFER CANNOT BE ACCEPTED IN RESPECT OF ARAN ADSs BY MEANS OF A FORM
OF ACCEPTANCE. A LETTER OF TRANSMITTAL FOR ACCEPTING THE OFFER IN RESPECT OF
ARAN ADSs CAN BE OBTAINED FROM THE US DEPOSITARY, THE IRISH RECEIVING AGENT OR
THE UK RECEIVING AGENT (AS EACH SUCH TERM IS DEFINED IN THE OFFER DOCUMENT).
 
   In all cases, payment for Aran shares purchased pursuant to the Offer will
be made only after timely receipt by the US Depositary, the Irish Receiving
Agent or the UK Receiving Agent (as each such term is defined in the Offer
Document) of a properly completed and duly executed Form of Acceptance,
together with the share certificates and/or other documents of title.
 
   Additional copies of the enclosed materials may be obtained from the US
Depositary, the Irish Receiving Agent or the UK Receiving Agent at their
respective addresses and telephone numbers set forth in the Offer Document.
 
   Terms defined in the Offer Document shall have the same meanings in this
letter.
 
                               Very truly yours,
 
                                Rothschild Inc.
                          1251 Avenue of the Americas
                                  51st Floor
                              New York, NY 10020
                      (212) 403-3611 within New York City
          (800) 753-5151 ext. 3611 (Toll Free) outside New York City
 

<PAGE>

                                                                EXHIBIT 99(a)(7)
 
   The document should not be forwarded or transmitted in or into Australia,
                               Canada or Japan.
 
ROTHSCHILD INC.
 
                   OFFER FOR ALL OUTSTANDING ORDINARY SHARES

                        AND AMERICAN DEPOSITARY SHARES

                                      OF

                                ARAN ENERGY PLC

                                      BY

                         N M ROTHSCHILD & SONS LIMITED

                                 ON BEHALF OF

                           ARCO IRISH HOLDINGS INC.

                      (A WHOLLY OWNED SUBSIDIARY OF ARCO)
 
 THE OFFER IS OPEN FOR ACCEPTANCE UNTIL 3:00 P.M. (DUBLIN AND LONDON TIME),
 10:00 A.M. (NEW YORK CITY TIME), ON SEPTEMBER 23, 1995 (THE "INITIAL
 PERIOD"), UNLESS EXTENDED (IN ACCORDANCE WITH THE TERMS THEREOF. AT THE
 CONCLUSION OF THE INITIAL PERIOD OR ON OR BEFORE THE CONCLUSION OF ANY
 EXTENSION THEREOF AND ON THE SATISFACTION OR, WHERE PERMITTED, WAIVER OF THE
 CONDITION(S) TO THE OFFER, THE PURCHASE OF ALL ARAN SECURITIES IN RESPECT OF
 WHICH THE OFFER HAS BEEN VALIDLY ACCEPTED AND NOT WITHDRAWN WILL TAKE PLACE,
 AND THE OFFER WILL BE EXTENDED FOR A SUBSEQUENT PERIOD OF AT LEAST FOURTEEN
 CALENDAR DAYS. PRIOR TO THE OFFER BECOMING OR OTHERWISE BEING DECLARED
 UNCONDITIONAL IN ALL RESPECTS, ACCEPTING ARAN SECURITYHOLDERS WILL HAVE THE
 RIGHT TO WITHDRAW THEIR ACCEPTANCES IN RESPECT THEREOF. HOWEVER, IN THE
 EVENT OF THE OFFER BECOMING OR BEING DECLARED UNCONDITIONAL IN ALL RESPECTS,
 NO RIGHTS OF WITHDRAWAL WILL BE AVAILABLE TO ACCEPTING ARAN SECURITYHOLDERS
 IN THE SUBSEQUENT PERIOD DURING WHICH THE OFFER REMAINS OPEN FOR ACCEPTANCE.
 
                                                                August 25, 1995
 
To holders of Aran ADSs (as defined below):
 
   Rothschild Inc. has been appointed by ARCO Irish Holdings ("ARCO Irish
Holdings") to act as dealer manager in the United States (the "US Dealer
Manager") in connection with an offer by N M Rothschild & Sons Limited, acting
in the United States through Rothschild Inc., and on behalf of ARCO Irish
Holdings, to purchase, upon the terms and subject to the conditions set forth
in the offer document dated August 25, 1995 (the "Offer Document") and the
accompanying Acceptance Forms (collectively, the "Offer"), all outstanding
ordinary shares of IR20p each ("Aran shares") of Aran Energy plc ("Aran") for
IR60p in cash, including all Aran shares represented by Aran American
Depositary Shares ("Aran ADSs"), each representing thirty Aran shares and
evidenced by Aran American Depositary Receipts ("Aran ADRs"), for
IR(Pounds)18.00 in cash. The Offer will extend to any Aran shares and Aran
ADSs unconditionally allotted or issued fully paid prior to the date on which
the Offer becomes or is declared unconditional (or such later date or dates as
ARCO Irish Holdings may decide) pursuant to the exercise of options granted
under Aran share option sheme(s) (as discussed in the Offer Document).
<PAGE>

2

   We are enclosing the following documents:
 
   1.  The Offer Document;
 
   2.  The Letter of Transmittal to be used by holders of Aran ADSs
       accepting the Offer;
 
   3.  The Notice of Guaranteed Delivery;
 
   4.  Guidelines for Certification of Taxpayer Identification Number on
       Substitute Form W-9; and
 
   5.  The return envelope addressed to the US Depositary.
 
   THE OFFER CANNOT BE ACCEPTED IN RESPECT OF ARAN SHARES (OTHER THAN ARAN
SHARES REPRESENTED BY ARAN ADSs) BY MEANS OF A LETTER OF TRANSMITTAL. A FORM
OF ACCEPTANCE FOR ACCEPTING THE OFFER IN RESPECT OF ARAN SHARES (OTHER THAN
ARAN SHARES REPRESENTED BY ARAN ADSs) CAN BE OBTAINED FROM THE US DEPOSITARY,
THE IRISH RECEIVING AGENT OR THE UK RECEIVING AGENT (AS EACH SUCH TERM IS
DEFINED IN THE OFFER DOCUMENT).
 
   In all cases, payment for Aran ADSs purchased pursuant to the Offer will be
made only after receipt by the US Depositary (as defined in the Offer
Document) of Aran ADRs evidencing such Aran ADSs or a confirmation of book-
entry transfer, together with the Letter of Transmittal (or a facsimile copy
thereof) properly completed and duly executed, and any other documents
required by the Letter of Transmittal.
 
   Additional copies of the enclosed materials may be obtained from the US
Depositary, the Irish Receiving Agent or the UK Receiving Agent at their
respective addresses and telephone numbers set forth in the Offer Document.
 
   Terms defined in the Offer Document shall have the same meanings in this
letter.
 
                               Very truly yours,
 
                                Rothchild Inc.
                          1251 Avenue of the Americas
                                  51st Floor
                              New York, NY 10020
                      (212) 403-3611 within New York City
          (800) 753-5151 ext. 3611 (Toll Free) outside New York City
 

<PAGE>

                                                                EXHIBIT 99(a)(8)
 
  This document should not be forwarded or transmitted in or into Australia,
                               Canada or Japan.
 
                   OFFER FOR ALL OUTSTANDING ORDINARY SHARES

                        AND AMERICAN DEPOSITARY SHARES

                                      OF

                                ARAN ENERGY PLC

                                      BY

                         N M ROTHSCHILD & SONS LIMITED

                                 ON BEHALF OF

                           ARCO IRISH HOLDINGS INC.

                      (A WHOLLY OWNED SUBSIDIARY OF ARCO)
 
 THE OFFER IS OPEN FOR ACCEPTANCE UNTIL 3:00 P.M. (DUBLIN AND LONDON TIME),
 10:00 A.M. (NEW YORK CITY TIME), ON SEPTEMBER 23, 1995 (THE "INITIAL
 PERIOD"), UNLESS EXTENDED (IN ACCORDANCE WITH THE TERMS THEREOF). AT THE
 CONCLUSION OF THE INITIAL PERIOD OR ON OR BEFORE THE CONCLUSION OF ANY
 EXTENSION THEREOF AND ON THE SATISFACTION OR, WHERE PERMITTED, WAIVER OF THE
 CONDITION(S) TO THE OFFER, THE PURCHASE OF ALL ARAN SECURITIES IN RESPECT OF
 WHICH THE OFFER HAS BEEN VALIDLY ACCEPTED AND NOT WITHDRAWN WILL TAKE PLACE,
 AND THE OFFER WILL BE EXTENDED FOR A SUBSEQUENT PERIOD OF AT LEAST FOURTEEN
 CALENDAR DAYS. PRIOR TO THE OFFER BECOMING OR OTHERWISE BEING DECLARED
 UNCONDITIONAL IN ALL RESPECTS, ACCEPTING ARAN SECURITYHOLDERS WILL HAVE THE
 RIGHT TO WITHDRAW THEIR ACCEPTANCES IN RESPECT THEREOF. HOWEVER, IN THE
 EVENT OF THE OFFER BECOMING OR BEING DECLARED UNCONDITIONAL IN ALL RESPECTS,
 NO RIGHTS OF WITHDRAWAL WILL BE AVAILABLE TO ACCEPTING ARAN SECURITYHOLDERS
 IN THE SUBSEQUENT PERIOD DURING WHICH THE OFFER REMAINS OPEN FOR ACCEPTANCE.
 
                                                                August 25, 1995
 
To Our Clients:
 
   Enclosed for your consideration is the offer document dated August 25, 1995
(the "Offer Document"), the Letter of Transmittal and Notice of Guaranteed
Delivery relating to an offer by N M Rothschild & Sons Limited, acting in the
United States through Rothschild Inc., and on behalf of ARCO Irish Holdings
Inc. ("ARCO Irish Holdings"), to purchase, upon the terms and subject to the
conditions set forth in the Offer Document and the accompanying Acceptance
Forms (as defined in the Offer Document) (collectively, the "Offer"), all
outstanding ordinary shares of IR20p each ("Aran shares") of Aran Energy plc
("Aran") for IR60p in cash, including all Aran shares represented by Aran
American Depositary Shares ("Aran ADSs"), each representing thirty Aran shares
and evidenced by Aran American Depositary Receipts ("Aran ADRs"), for
IR(Pounds)18.00 in cash. The Offer will extend to any Aran shares and Aran
ADSs unconditionally allotted or issued fully paid prior to the date on which
the Offer becomes or is declared unconditional (or such later date or dates as
ARCO Irish Holdings may decide) pursuant to the exercise of options granted
under Aran share option scheme(s) (as discussed in the Offer Document).
 
   We are the holder of record of Aran ADSs held by us for your account. An
acceptance of the Offer in respect of such Aran ADSs can be made only by us as
the holder of record and pursuant to your instructions. Accordingly, we
request instructions as to whether you wish to have us accept the Offer on
your behalf in respect of any or all Aran ADSs held by us for your account
pursuant to the terms and subject to the conditions set forth in the Offer.
<PAGE>

2 
   Your attention is invited to the following:
 
   1.  The Offer is conditional upon the satisfaction or, where permissible,
       waiver by ARCO Irish Holdings of certain conditions set forth in
       Appendix 1 to the Offer Document.
 
   2.  The Initial Period of the Offer will expire at 3:00 p.m. (Dublin and
       London time), 10:00 a.m. (New York City time) on September 23, 1995,
       unless extended (in accordance with the terms thereof).
 
   3.  Any stock transfer taxes applicable to a sale of Aran ADSs to ARCO
       Irish Holdings will be borne by ARCO Irish Holdings except as
       otherwise provided in Instruction 6 of the Letter of Transmittal.
 
   THE OFFER CANNOT BE ACCEPTED IN RESPECT OF ARAN SHARES (OTHER THAN ARAN
SHARES REPRESENTED BY ARAN ADSs) BY MEANS OF A LETTER OF TRANSMITTAL. A FORM
OF ACCEPTANCE FOR ACCEPTING THE OFFER IN RESPECT OF ARAN SHARES (OTHER THAN
ARAN SHARES REPRESENTED BY ARAN ADSs) MAY BE OBTAINED FROM THE US DEPOSITARY,
THE IRISH RECEIVING AGENT OR THE UK RECEIVING AGENT (AS EACH SUCH TERM IS
DEFINED IN THE OFFER DOCUMENT).
 
   If you wish to have us accept the Offer in respect of any or all of the
Aran ADSs held by us for your account, please so instruct us by completing,
executing and returning to us the instruction form contained in this letter.
If you authorize us to accept the Offer in respect of your Aran ADSs, the
Offer will be accepted in respect of all such Aran ADSs unless otherwise
indicated in such instruction form. Please forward your instruction form to us
in ample time to permit us to accept the Offer on your behalf prior to the
expiration of the Offer. The specimen Letter of Transmittal is furnished to
you for your information only and cannot be used by you to accept the Offer in
respect of Aran ADSs held by us for your account.
 
<PAGE>

3
 
                  INSTRUCTIONS WITH RESPECT TO THE OFFER FOR
                   ALL OUTSTANDING ARAN SHARES AND ARAN ADSs
 
   The undersigned acknowledge(s) receipt of your letter and the offer
document dated August 25, 1995 (the "Offer Document"), the Letter of
Transmittal and Notice of Guaranteed Delivery relating to an offer by N M
Rothschild & Sons Limited, acting in the United States through Rothschild
Inc., and on behalf of ARCO Irish Holdings Inc. to purchase, upon the terms
and subject to the conditions set forth in the Offer Document and the
accompanying Acceptance Forms (collectively, the "Offer") all outstanding
ordinary shares of IR20p each ("Aran shares") of Aran Energy plc ("Aran") for
IR60p in cash, including all Aran shares represented by Aran American
Depositary Shares ("Aran ADSs"), each representing thirty Aran shares and
evidenced by Aran American Depositary Receipts, for IR(Pounds)18.00 in cash.
 
   This will instruct you to accept the Offer in respect of the number of Aran
ADSs indicated below (or, if no number is indicated below, all Aran ADSs) held
by you for the account of the undersigned, upon the terms and subject to the
conditions set forth in the Offer.
 
Dated       , 1995
 
 Number of Aran ADSs accepting the Offer/1/
 
 
 ______ Aran ADSs
                                       ---------------------------------------

                                       ---------------------------------------
                                                    Signature(s)


                                       ---------------------------------------

                                       ---------------------------------------
                                                Please print name(s)


                                       ---------------------------------------

                                       ---------------------------------------
                                                     Address(es)


                                       ---------------------------------------
                                               Area Code and Tel. No.


                                       ---------------------------------------
                                          Employer Identification or Social
                                                    Security No.
 
---------------------
1.  Unless otherwise indicated, it will be assumed that the Offer is to be
    accepted in respect of all your Aran ADSs.

<PAGE>

                                                                EXHIBIT 99(a)(9)

            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9
 
GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE
PAYER.--Social Security numbers have nine digits separated by two hyphens:
i.e. 000-00-0000. Employer identification numbers have nine digits separated
by only one hyphen: i.e. 00-0000000. The table below will help determine the
number to give the payer.
 
<TABLE>
<CAPTION> 
-----------------------------------------
                        GIVE THE
 FOR THIS TYPE OF       SOCIAL SECURITY
 ACCOUNT:               NUMBER OF--
-----------------------------------------
 <C> <S>                <C>
 1.  An individual's    The individual
     account

 2.  Two or more        The actual owner
     individuals        of the account
     (joint account)    or, if combined
                        funds, any one of
                        the
                        individuals(1)

 3.  Husband and wife   The actual owner
     (joint account)    of the account
                        or, if joint
                        funds, either
                        person(1)

 4.  Custodian          The minor(2)
     account of a
     minor (Uniform
     Gift to Minors
     Act)

 5.  Adult and minor    The adult or, if
     (joint account)    the minor is the
                        only contributor,
                        the minor(1)

 6.  Account in the     The ward, minor,
     name of guardian   or incompetent
     or committee for   person(3)
     a designated
     ward, minor, or
     incompetent
     person

 7.  a. The usual       The grantor-
        revocable       trustee(1)
        savings trust
        account
        (grantor is
        also trustee)

     b. So-called       The actual
        trust account   owner(1)
        that is not a
        legal or
        valid trust
        under State
        law

 8.  Sole               The owner(4)
     proprietorship
     account
<CAPTION> 
-----------------------------------------
                        GIVE THE EMPLOYER
 FOR THIS TYPE OF       IDENTIFICATION
 ACCOUNT:               NUMBER OF--
-----------------------------------------
 <C> <S>                <C>
 9.  A valid trust,     The legal entity
     estate, or         (Do not furnish
     pension trust      the identifying
                        number of the
                        personal
                        representative or
                        trustee unless
                        the legal entity
                        itself is not
                        designated in the
                        account title.)(5)

10.  Corporate account  The corporation

11.  Religious,         The organization
     charitable, or 
     educational 
     organization 
     account                                            

12.  Partnership        The partnership
     account held in 
     the name of the 
     business                                                  

13.  Association, club, The organization
     or other 
     tax-exempt 
     organization                                                   

14.  A broker or        The broker or nominee
     registered 
     nominee 
                                  
15.  Account with the   The public entity
     Department of 
     Agriculture in the 
     name of a public 
     entity (such as a 
     State or local   
     government, school 
     district, or 
     prison) that 
     receives 
     agricultural 
     program payments
</TABLE>
-----------------------------------------
 
(1) List first and circle the name of the person whose number you furnish.
(2) Circle the minor's name and furnish the minor's social security number.
(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.
(4) Show the individual name of the owner, but the business or "doing business
    as" name may be entered in addition. Either the social security number of
    the individual owner or the employer identification number of the sole
    proprietorship may be used.
(5) List first and circle the name of the legal trust, estate, or pension
    trust.
 
NOTE:  If no name is circled when there is more than one name, the number will
       be considered to be that of the first name listed.
<PAGE>
 
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9

                                    PAGE 2
OBTAINING A NUMBER

If you don't have a taxpayer identification number or you don't know your
number, obtain Form SS-5, Application for a Social Security Number Card, or
Form SS-4, Application for Employer Identification Number, at the local office
of the Social Security Administration or the Internal Revenue Service and
apply for a number.
 
PAYEES AND PAYMENTS EXEMPT FROM BACKUP WITHHOLDING

The following is a list of payees exempt from backup withholding and for which
no information reporting is required. For interest and dividends, all listed
payees are exempt except item (9). For broker transactions, payees listed in
items (1) through (13) and a person registered under the Investment Advisers
Act of 1940 who regularly acts as a broker are exempt. Payments subject to
reporting under sections 6041 and 6041A are generally exempt from backup
withholding only if made to payees described in items (1) through (7), except
a corporation that provides medical and health care services or bills and
collects payments for such services is not exempt from backup withholding or
information reporting. Only payees described in items (2) through (6) are
exempt from backup withholding for barter exchange transactions, patronage
dividends, and payments by certain fishing boat operators.

 (1) A corporation.

 (2) An organization exempt from tax under section 501(a), or an IRA, or a
     custodial account under section 403(b)(7).

 (3) The United States or any of its agencies or instrumentalities.

 (4) A state, the District of Columbia, a possession of the United States, or
     any of their political subdivisions or instrumentalities.

 (5) A foreign government or any of its political subdivisions, agencies, or
     instrumentalities.

 (6) An international organization or any of its agencies or instrumentali-
     ties.

 (7) A foreign central bank of issue.

 (8) A dealer in securities or commodities required to register in the United
     States or a possession of the United States.

 (9) A futures commission merchant registered with the Commodity Futures
     Trading Commission.

(10) A real estate investment trust.

(11) An entity registered at all times during the tax year under the Invest-
     ment Company Act of 1940.

(12) A common trust fund operated by a bank under section 584(a).

(13) A financial institution.

(14) A middleman known in the investment community as a nominee or listed in
     the most recent publication of the American Society of Corporate Secre-
     taries, Inc., Nominee List.

(15) A trust exempt from tax under section 664 or described in section 4947.
 
  Payments of dividends and patronage dividends generally not subject to
backup withholding include the following:

 . Payments to nonresident aliens subject to withholding under section 1441.

 . Payments to partnerships not engaged in a trade or business in the United
   States and which have at least one nonresident partner.

 . Payments of patronage dividends where the amount received is not paid in
   money.

 . Payments made by certain foreign organizations.
 
  Payments of interest generally not subject to backup withholding include the
following:

 . Payments of interest on obligations issued by individuals. Note: You may
   be subject to backup withholding if this interest is $600 or more and is
   paid in the course of the payer's trade or business and you have not
   provided your correct taxpayer identification number to the payer.

 . Payments of tax-exempt interest (including exempt-interest dividends under
   section 852).

 . Payments described in section 6049(b)(5) to non-resident aliens.

 . Payments on tax-free covenant bonds under section 1451.

 . Payments made by certain foreign organizations.
 
Exempt payees described above should file Form W-9 to avoid possible erroneous
backup withholding. FILE THIS FORM WITH THE PAYER, FURNISH YOUR TAXPAYER IDEN-
TIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE OF THE FORM, SIGN AND DATE THE
FORM AND RETURN IT TO THE PAYER.
 
  Payments that are not subject to information reporting are also not subject
to backup withholding. For details, see sections 6041, 6041A(a), 6042, 6044,
6045, 6049, 6050A, and 6050N, and their regulations.
 
PRIVACY ACT NOTICE.--Section 6109 requires you to give your correct taxpayer
identification number to persons who must file information returns with the
IRS to report interest, dividends, and certain other income paid to you,
mortgage interest you paid, the acquisition or abandonment of secured
property, cancellation of debt, or contributions you made to an IRA. The IRS
uses the numbers for identification purposes and to help verify the accuracy
of your tax return. You must provide your taxpayer identification number
whether or not you are required to file a tax return. Payers must generally
withhold 31% of taxable interest, dividend, and certain other payments to a
payee who does not give a taxpayer identification number to a payer. Certain
penalties may also apply.
 
PENALTIES.

(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER.--If you
fail to furnish your correct taxpayer identification number to a payer, you
are subject to a penalty of $50 for each such failure unless your failure is
due to reasonable cause and not to willful neglect.

(2) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING.--If you
make a false statement with no reasonable basis that results in no backup
withholding, you are subject to a penalty of $500.

(3) CRIMINAL PENALTY FOR FALSIFYING INFORMATION.--Willfully falsifying
certifications or affirmations may subject you to criminal penalties including
fines and/or imprisonment.

(4) MISUSE OF TAXPAYER IDENTIFICATION NUMBERS.--If the payer discloses or uses
taxpayer identification numbers in violation of Federal law, the payer may be
subject to civil and criminal penalties.
 
FOR ADDITIONAL INFORMATION, CONTACT YOUR TAX CONSULTANT OR THE INTERNAL
REVENUE SERVICE.

<PAGE>
 
                                                              EXHIBIT 99.(a)(10)

                                    [LOGO]

                  LETTERHEAD OF N M ROTHSCHILD & SONS LIMITED

                                 PRESS RELEASE

NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO CANADA, JAPAN OR
AUSTRALIA



EMBARGOED UNTIL 7.30 AM                                           21 August 1995



                            ARCO IRISH HOLDINGS INC.
                            ("ARCO IRISH HOLDINGS")


                          A WHOLLY OWNED SUBSIDIARY OF


                           ATLANTIC RICHFIELD COMPANY
                                    ("ARCO")


                        IR(Pounds)157 MILLION CASH OFFER


                                      FOR


                                ARAN ENERGY PLC
                                    ("ARAN")







                New Court, St. Swithin's Lane, London EC4P 4DU
   Telephone 0171-280 5000        Fax 0171-929 1643         Telex 888031

                               Regulated by SFA
<PAGE>

                                     -2-
 
THE BOARD OF ARCO IRISH HOLDINGS, A WHOLLY OWNED SUBSIDIARY OF ARCO, ANNOUNCES
THE TERMS OF A CASH OFFER TO BE MADE ON ITS BEHALF BY N M ROTHSCHILD & SONS
LIMITED TO ACQUIRE THE WHOLE OF ARAN'S ISSUED (AND TO BE ISSUED) SHARE CAPITAL
(INCLUDING ARAN SHARES REPRESENTED BY ARAN ADSs).
<TABLE>
<CAPTION>
 
THE OFFER:
<S>                                                  <C>      
 
 . VALUES THE ISSUED SHARE CAPITAL                    IR(Pounds)157 MILLION
  OF ARAN AT APPROXIMATELY                           (STG(Pounds)161MILLION)*
 
 . FOR EACH ARAN SHARE                                IR60p IN CASH
                                                     (STG61.4P)*
 
 . FOR EACH ARAN ADS                                  IR(Pounds)18.00 IN CASH
  (EACH ADS REPRESENTS 30 ARAN SHARES)               ($28.44)*

 . PREMIUM OVER ARAN'S LAST DEALT PRICE
  IN DUBLIN ON 18 AUGUST 1995                        41 PER CENT.
  (THE LAST DEALING DAY BEFORE THIS ANNOUNCEMENT)

 . PREMIUM OVER ARAN'S PAST FOUR YEAR SHARE PRICE
  HIGH IN DUBLIN                                     28 PER CENT.

 . PROVIDES AN OPPORTUNITY FOR ARAN SHAREHOLDERS TO GENERATE INCOME ON THEIR
  CAPITAL
</TABLE> 

(*EQUIVALENT, BASED ON EXCHANGE RATES SET OUT IN APPENDIX 2.)


BILL WADE, EXECUTIVE DIRECTOR OF ARCO, RESPONSIBLE FOR WORLDWIDE EXPLORATION AND
PRODUCTION, SAID:

     "ARCO IS COMMITTED TO EXPANDING ITS OPERATIONS INTERNATIONALLY.  ARCO HAS
     BEEN ACTIVE IN NORTHWEST EUROPE FOR MORE THAN 30 YEARS AND THE PROPOSED
     ACQUISITION OF ARAN FITS ARCO'S STRATEGY OF EXPANDING ITS PRESENCE IN THIS
     CORE REGION.

     WE BELIEVE OUR CASH OFFER IS A FULL AND GENEROUS ONE. WE HOPE THE BOARD OF
     ARAN WILL RECOGNISE THE MERITS OF OUR OFFER AND RECOMMEND ACCEPTANCE OF IT
     AS BEING IN THE INTERESTS OF ARAN AND ITS SHAREHOLDERS."
<PAGE>
 
PRESS ENQUIRIES:
 
ARCO
Bill Wade                               Telephone:   (353) 1 496 0244
Terry Dallas                            Telephone:   (44) 171 831 3113
 
N M ROTHSCHILD & SONS LIMITED           Telephone:   (44) 171 280 5000
Nicholas Wrigley
Tony Allen
 
PUBLIC RELATIONS:
 
WHPR                                    Telephone:   (353) 1 496 0244
Brian Bell
 
FINANCIAL DYNAMICS
Nick Miles                              Telephone:   (44) 171 831 3113
Marc Popiolek                           Telephone:   (44) 171 831 3113
Sean Bellew                             Telephone:   (353) 1 496 0244
<PAGE>
 
NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO CANADA, JAPAN OR
AUSTRALIA



EMBARGOED UNTIL 7.30 AM                                           21 August 1995



                            ARCO IRISH HOLDINGS INC.
                            ("ARCO IRISH HOLDINGS")

                          A WHOLLY OWNED SUBSIDIARY OF

                           ATLANTIC RICHFIELD COMPANY
                                    ("ARCO")

                        IR(Pounds)157 MILLION CASH OFFER
                                      FOR

                                ARAN ENERGY PLC
                                    ("ARAN")


The Board of ARCO Irish Holdings, a wholly owned subsidiary of ARCO, announces
the terms of a cash offer to be made on its behalf by N M Rothschild & Sons
Limited to acquire the whole of Aran's issued (and to be issued) share capital
(including Aran shares represented by Aran ADSs).

The Offer values the existing issued share capital of Aran at approximately
IR(Pounds)157 million (equivalent to Stg(Pounds)161 million).

The brokers to the Offer are Riada Corporate Finance Limited and Hoare Govett
Corporate Finance Limited.

REASONS FOR THE OFFER

ARCO is one of the world's leading integrated oil and gas companies.  ARCO and
its affiliates have major operations in the US, UK, the Netherlands, Indonesia
and Australia.  In addition, ARCO has exploration and production operations in
16 other countries including Ireland.  ARCO and its affiliates employ
approximately 23,000 people worldwide.
<PAGE>
 
                                      -2-

ARCO has been active in the UK North Sea and in the waters surrounding Ireland
since 1964 and 1985 respectively.  In the UK, ARCO has actively participated
since the first licence round with $1.9 billion invested in exploration and
development activities, and has been involved in exploration activities on 16
Irish blocks with expenditure in Ireland of over $14 million.

Historically, ARCO's producing assets were predominantly US based.  For a number
of years, ARCO has pursued a strategy of expanding globally its exploration and
production operations.  The acquisition of Aran, which would add complementary
assets in the core area of Northwest Europe, is a positive step in support of
this strategy.

The Offer takes full account of the value of Aran's two largest producing
assets, Alba and Gryphon, as determined by recent auction sales of interests in
those fields.  The Offer also provides significant value for the balance of
Aran's portfolio which is characterised by its higher risk non-producing
appraisal and exploration assets, which include the Schiehallion and Connemara
oil fields that lie offshore the west of Shetlands and Ireland respectively.

ARCO has both the financial and technical resources to carry the risk and
exploit these assets successfully.  ARCO has the resources to carry out the
expeditious appraisal and, if justified, the development of the Connemara
discovery off Western Ireland.

THE OFFER

The Offer, which will be subject to the conditions and further terms set out
below and in Appendix 1, will be made on the following bases:

FOR EACH ORDINARY
SHARE OF IR20p OF ARAN                      IR60p IN CASH
("ARAN SHARE")
 
FOR EACH ARAN ADS                           IR(Pounds)18.00 IN CASH
(WHICH REPRESENTS 30 ARAN SHARES)

Based on an exchange rate of IR(Pounds)1=Stg(Pounds)1.023, the Offer represents
Stg61.4p per Aran share and Stg(Pounds)18.42 per Aran ADS.  Based on an exchange
rate of IR(Pounds)1=$1.5802, the Offer represents $0.95 per Aran share and
$28.44 per Aran ADS.  Appendix 2 sets out the details of such exchange rates.

<PAGE>
 
                                      -3-

On the bases set out in Appendix 2:

 .    the Offer values the existing issued share capital of Aran (including Aran
     shares represented by Aran ADSs) at approximately IR(Pounds)157 million
     (equivalent to approximately Stg(Pounds)161 million).

 .    the Offer represents a premium of 41 per cent. over the last dealt price in
     Dublin of IR42.5p per Aran share on 18 August 1995, the last business day
     before this announcement.

 .    the Offer represents a premium of 28 per cent. over the Aran share price
     high in Dublin over the last four years of IR47p per share.

Aran has never paid a dividend.  Accordingly, the Offer provides an opportunity
for Aran shareholders to generate income on their capital.

Further details of the financial effects of the Offer are set out in Appendix 3.

TERMS AND CONDITIONS

The Aran shares (including Aran shares represented by Aran ADSs) which are the
subject of the Offer will be acquired by ARCO Irish Holdings free from all
liens, equitable interests, charges and encumbrances and together with all
rights now or hereafter attaching thereto, including voting rights and the right
to receive and retain all dividends and other distributions declared, made or
paid on or after the date of this announcement.

Whilst the Offer is denominated in Irish pounds, accepting Aran shareholders and
holders of Aran ADSs will be entitled to receive their cash consideration in
Irish pounds or either sterling or US dollars at prevailing exchange rates on
the latest practicable business day preceding the date of payment.

If the Offer becomes unconditional and sufficient acceptances are received, ARCO
Irish Holdings intends to apply the provisions of Section 204 of the Irish
Companies Act to acquire compulsorily any outstanding Aran shares (including
Aran shares represented by ADSs) not acquired pursuant to the Offer or
otherwise.

The Offer will be subject to the conditions and further terms set out in
Appendix 1 and in the formal offer document.  Certain words and expressions used
in this announcement are defined in Appendix 4.

<PAGE>
 
                                     -4-
 
THE BUSINESS OF ARCO

ARCO is a worldwide, integrated hydrocarbons corporation with operations and
subsidiaries encompassing all aspects of the oil and gas business including
exploration, production and marketing of crude oil, natural gas and natural gas
liquids, and refining, marketing and transportation of petroleum products. ARCO
also mines and markets coal and has interests in two petrochemical companies. It
is based in California and has major operations in Alaska, California,
Washington and the Gulf Coast as well as in the UK, the Netherlands, Indonesia
and Australia and employs approximately 23,000 people worldwide. ARCO's common
stock is listed on the New York, Zurich and London Stock Exchanges.

For the year ended 31 December 1994, ARCO reported consolidated net income after
tax of $919 million on consolidated total revenue of $17.2 billion. Consolidated
stockholders' equity as at 31 December 1994 amounted to $6.3 billion. In the six
months to 30 June 1995, ARCO reported unaudited consolidated net income after
tax of $713 million on unaudited consolidated total revenue of $9.1 billion.
Unaudited consolidated stockholders' equity as at 30 June 1995 amounted to $6.6
billion.

Further information on ARCO is set out in Appendix 5.

ARCO IRISH HOLDINGS

ARCO Irish Holdings is a wholly owned subsidiary of ARCO, incorporated in
Delaware, US on 2 August 1995 for the purpose of making the Offer. To date, ARCO
Irish Holdings has engaged in no activities other than those incidental to its
organisation and the making of the Offer.

THE BUSINESS OF ARAN

Aran explores for, develops and produces oil and gas. The Aran Group's principal
activities are in the UK offshore sector (including the North Sea), the US Gulf
Coast area and offshore Ireland. Aran's registered office is in Dublin, Ireland,
and Aran has its principal operating units in London and Houston. Aran shares
are listed on the Irish Stock Exchange and the London Stock Exchange and Aran
ADSs are quoted on NASDAQ.

For the year ended 31 December 1994, Aran reported an after tax profit of
IR(Pounds)3.7 million on turnover of IR(Pounds)83.4 million and had consolidated
shareholders' funds at that date of IR(Pounds)80.0 million.  It employed an
average of 39 people during 1994.

Further information on Aran is set out in Appendix 6.

<PAGE>
 
                                      -5-

MANAGEMENT AND EMPLOYEES

The existing employment rights, including pension rights, of the management and
employees of the Aran Group will be fully safeguarded.

ARAN SHARE OPTION SCHEME(S)

The Offer will extend to any Aran securities unconditionally allotted or issued
prior to the date on which the Offer becomes or is declared unconditional (or
such later date as ARCO Irish Holdings may decide) pursuant to the exercise of
options granted under the Aran share option scheme(s). Appropriate proposals
will be made by ARCO Irish Holdings in due course to holders of options under
the Aran share option scheme(s).

GENERAL

Neither ARCO, nor any of the subsidiaries or the directors of ARCO, nor, so far
as ARCO is aware, any party acting in concert with ARCO, owns or controls any
Aran shares or Aran ADSs or holds any options to purchase Aran shares or Aran
ADSs.  In the interests of confidentiality, ARCO has not made enquiries in this
respect of certain of the parties who may be deemed by the Panel to be acting in
concert with ARCO Irish Holdings for the purposes of the Offer.

POSTING OF DOCUMENTS TO SHAREHOLDERS

Rothschilds, which is acting as financial adviser to ARCO and ARCO Irish
Holdings, will despatch the formal offer document and Acceptance Forms to Aran
shareholders as soon as possible.  Rothschilds will be acting through Rothschild
Inc. for the purpose of making the Offer in the United States.


                                    - ENDS -

<PAGE>
 
                                      -6-

PRESS ENQUIRIES:
 
ARCO
Bill Wade                          Telephone:   (353) 1 496 0244
Terry Dallas                       Telephone:   (44) 171 831 3113
 
N M ROTHSCHILD & SONS LIMITED      Telephone:   (44) 171 280 5000
Nicholas Wrigley
Tony Allen
 
WHPR                               Telephone:   (353) 1 496 0244
Brian Bell
 
FINANCIAL DYNAMICS
Nick Miles                         Telephone:   (44) 171 831 3113
Marc Popiolek                      Telephone:   (44) 171 831 3113
Sean Bellew                        Telephone:   (353) 1 496 0244
 
N M Rothschild & Sons Limited, Hoare Govett Corporate Finance Limited, which are
both regulated by The Securities and Futures Authority Limited in the UK, and
Riada Corporate Finance Limited are acting for the ARCO Group in connection with
the Offer and no one else and will not be responsible to anyone other than the
ARCO Group for providing the protections afforded to their respective customers
or for providing advice in relation to the Offer.

This announcement does not constitute an offer or invitation to purchase any
securities.

<PAGE>
 
                                      -7-

                                  APPENDIX 1

               CONDITIONS AND CERTAIN FURTHER TERMS OF THE OFFER


The Offer will be made in accordance with and subject to the provisions of the
City Code and the applicable rules and regulations of the SEC.

The Offer will be subject to the following conditions:

(a) valid acceptances being received (and not, where permitted, withdrawn) by
    3.00 p.m. (Dublin and London time), 10.00 a.m. (New York City time) on the
    first closing date of the Offer (or such later time(s) and/or date(s) as
    ARCO Irish Holdings may, subject to the rules of the City Code, decide) in
    respect of not less than 95 per cent (or such lesser percentage as ARCO
    Irish Holdings may decide) of the Aran shares to which the Offer relates
    provided that this condition shall not be satisfied unless ARCO Irish
    Holdings and/or its wholly owned subsidiaries shall have acquired or agreed
    to acquire, pursuant to the Offer or otherwise, Aran shares (including Aran
    shares represented by Aran ADSs) carrying more than 50 per cent. of the
    voting rights normally exercisable at general meetings of Aran, including,
    for this purpose any such voting rights attaching (or which on issue will
    attach) to any Aran shares (including Aran shares represented by Aran ADSs)
    unconditionally allotted or issued before this condition is satisfied
    whether pursuant to the exercise of any outstanding subscription or
    conversion rights or otherwise; and for this purpose the expression "Aran
    shares to which the Offer relates" means the aggregate of Aran shares
    (including Aran shares represented by Aran ADSs) which have been
    unconditionally allotted or issued before the date on which the Offer is
    made and Aran shares allotted after that date but on or before the date upon
    which the Offer becomes or is declared unconditional (or such later date as
    ARCO Irish Holdings may decide) but excluding Aran shares which at the date
    of the Offer were in the beneficial ownership or deemed to be in the
    beneficial ownership (under Section 204 of the Irish Companies Act) of ARCO
    Irish Holdings;

(b) the Minister for Enterprise and Employment of Ireland having stated in
    writing that he does not intend to make an order under Section 9 of the
    Mergers, Take-overs and Monopolies (Control) Act, 1978 (as amended) of
    Ireland (the "Mergers Act") in relation to the Offer or, in the event of the
    said Minister making an order subject to conditions, ARCO Irish Holdings in
    its absolute discretion having decided to accept such conditions or, in the
    event of no such order being made and the said Minister not stating in
    writing that he does not intend to make such an order, the relevant period
    within the meaning of section 6 of the Mergers Act having expired;

(c) the Minister for Transport, Energy and Communications of Ireland granting
    such assurances, confirmations, consents, approvals or authorisations as may
    be required to ensure that none of the petroleum prospecting licences,
    licensing options, exploration licences, lease undertakings, petroleum
    leases and/or reserved area licences held by Aran and/or any other member of
    the Wider Aran Group will be revoked, altered or terminated as a result of
    the Offer or the acquisition of Aran securities by ARCO Irish Holdings
    pursuant to the Offer;

(d) it being established in terms satisfactory to ARCO Irish Holdings that the
    proposed acquisition of Aran by ARCO Irish Holdings or any matters arising
    therefrom will not be referred to the UK Monopolies and Mergers Commission;

(e) the SEC having given and not having rescinded or revoked, in whole or in
    part, any necessary or desirable exemptive relief under the US Exchange Act
    with respect to the Offer;

(f) the UK Department of Trade and Industry having given such assurances as may
    be required to ensure that none of the exploration or production licences
    held by Aran and/or any other members of the Wider Aran Group will be
    revoked, and that no further change in control of the licensee will be
    required, in each case as a result of the Offer or the proposed acquisition
    by ARCO Irish Holdings of any Aran shares (including Aran shares represented
    by Aran ADSs);

(g) ARCO Irish Holdings not having discovered that, except as disclosed in the
    accounts of Aran for the year ended 31 December 1994 or in any information
    which has been publicly announced by Aran prior to 17 August 1995:

    (i)    any past or present member of the Wider Aran Group has not complied 
           with all applicable legislation or regulations of any jurisdiction
           with regard to the disposal, discharge, spillage, leak or emission of
           any waste or hazardous substance or any substance likely to impair
           the environment or harm human health which non-compliance would be
           likely to give rise to a

<PAGE>
 
                                     -8-
 
           liability (whether actual or contingent) on the part of any member of
           the Wider Aran Group;

    (ii)   (1) there has been a disposal, spillage or leak of waste or hazardous
           substance or any substance likely to impair the environment or harm
           human health on; or

           (2) there has been an emission or discharge of any waste or hazardous
           substance or any substance likely to impair the environment or harm
           human health from, 

           any land or other asset now or previously owned, occupied or made use
           of by any past or present member of the Wider Aran Group which would
           be likely to give rise to a liability (whether actual or contingent)
           on the part of any member of the Wider Aran Group;

    (iii)  there is any liability (whether actual or contingent) to make good,
           repair, re-instate or clean up any property now or previously owned,
           occupied or made use of by any past or present member of the Wider
           Aran Group under any environmental legislation, regulation, notice,
           circular or order of any government, quasi-government, state or local
           government, supranational, statutory or regulatory body, court,
           agency or association or any other public body in any jurisdiction;
           or

    (iv)   circumstances exist whereby a person or class of persons would be 
           likely to have any claim or claims in respect of any oil and/or gas
           exploration, appraisal, development or production activities or any
           product or process of manufacture or materials used therein now or
           previously conducted, manufactured, sold or carried out by any past
           or present member of the Wider Aran Group which claim or claims would
           be likely to affect adversely any member of the Wider Aran Group;

    and any such matter is adverse to and material in the context of the Wider
    Aran Group;

(h) any necessary exchange control consents or clearances required to implement
    the Offer having been received;

(i) there being no provision of any agreement, arrangement, licence, permit,
    authorisation, royalty agreement or other instrument, including any joint
    venture agreement, to or of which any member of the Wider Aran Group or any
    partnership or company or other entity in which any member of the Wider Aran
    Group is interested (an "associate") is a party or has the benefit or by or
    to which any such member or associate or their assets may be bound, entitled
    or subject which, as a consequence of the Offer or the proposed acquisition
    by ARCO Irish Holdings of any Aran shares (including Aran shares represented
    by Aran ADSs) or control of Aran, or any part thereof, could or might result
    in:

    (i)    any monies borrowed by, or any other indebtedness, actual or 
           contingent, of, any such member or associate (other than pursuant to
           the Supplemental Agreement dated 29 June 1994 relating to a Facility
           Agreement dated 27 February 1992, each made between certain Aran
           Group companies and certain banks and other parties as specific
           therein) being or becoming repayable or capable of being declared
           repayable immediately or earlier than the repayment date provided for
           in such arrangement, agreement or instrument or the ability of any
           such member or associate to borrow monies or incur any indebtedness
           being withdrawn or inhibited;

    (ii)   any such agreement, arrangement, licence, permit, authorisation, 
           royalty agreement or instrument being terminated, revoked or modified
           or any obligation arising or any action being taken or arising
           thereunder;

    (iii)  the interests or business of any such member or associate in or with
           any person, firm, company or body (or any arrangements relating to
           such interests or business) being terminated or modified or affected;

    (iv)   any assets of any such member or associate being disposed of or
           charged otherwise than in the ordinary course of business;

    (v)    the creation of any mortgage, charge or other security interest over
           the whole or any part of the business, property or assets of any such
           member or associate or any such security, whenever arising or having
           arisen, becoming enforceable; or

    (vi)   the value of any member or associate of the Wider Aran Group or its
           financial or trading position being adversely affected; 

    and in any such case the result will be adverse to and material in the 
    context of the Wider Aran Group taken as a whole;

(j) no government or governmental, quasi-governmental, supranational, statutory
    or regulatory body, or any court, trade agency, association, institution or
    professional body or any other body or

<PAGE>
 
                                      -9-
 
    person whatsoever in any jurisdiction (including any foreign jurisdiction)
    having decided to take, instituted, implemented or threatened any action,
    proceedings, suit, investigation or enquiry (and in each case not having
    withdrawn such action, proceedings, suit, investigation or enquiry), or
    enacted, made or proposed any statute, regulation, decision or order (and in
    each case not having withdrawn the statute, regulation, decision or order)
    or taken any other steps which would or might:

    (i)    require or prevent the divestiture by any member of the ARCO Group or
           any member of the Wider Aran Group of all or any portion of their
           respective businesses, assets or property or impose any limitation on
           the ability of any of them to conduct their respective businesses and
           own any of their respective assets or property;

    (ii)   make the Offer or the acquisition of any Aran shares or control of 
           Aran by any member of the ARCO Group void, illegal, and/or
           unenforceable, or otherwise restrain, restrict, prohibit, delay or
           otherwise interfere with the implementation thereof, or impose
           additional conditions or obligations with respect thereto;

    (iii)  require any member of the ARCO Group or any member of the Wider Aran
           Group to offer to acquire any shares in any member of the Wider Aran
           Group owned by any third party;

    (iv)   impose any limitation on the ability of any member of the ARCO Group
           to acquire or hold or to exercise effectively any rights of ownership
           of shares in Aran or on the ability of Aran or any other member of
           the Wider Aran Group or any member of the ARCO Group to hold or
           exercise effectively any rights of ownership of shares in any member
           of the Wider Aran Group held or owned by it; or

    (v)    otherwise adversely affect the business, profits or prospects of any
           member of the ARCO Group or of the Wider Aran Group; 

    and all applicable waiting and other time periods during which any such
    government, governmental, quasi-governmental, supranational, statutory or
    regulatory body, court, trade agency, association, institution or
    professional body or person or body could institute any such action,
    proceedings, suit, investigation or enquiry having expired, lapsed or been
    terminated;

(k) all authorisations, orders, recognitions, grants, consents, licences,
    confirmations, clearances, permissions and approvals necessary or
    appropriate for or in respect of the Offer or proposed acquisition of any
    shares in, or control of, Aran by ARCO Irish Holdings having been obtained
    in terms and in a form satisfactory to ARCO Irish Holdings from all
    appropriate governments, governmental, quasi-governmental, supranational,
    statutory or regulatory bodies or courts, trade agencies, associations,
    institutions or professional bodies or from any bodies or persons whatsoever
    in any jurisdiction (including any foreign jurisdiction) with whom any
    member of the Aran Group has entered into contractual arrangements and such
    authorisations, orders, recognitions, grants, consents, licences,
    confirmations, clearances, permissions and approvals together with all
    authorisations, orders, recognitions, grants, licences, confirmations,
    clearances, permissions and approvals necessary or appropriate to carry on
    the business of any member of the Aran Group remaining in full force and
    effect at the time at which the Offer becomes otherwise unconditional and
    all necessary filings having been made for such purposes and all appropriate
    waiting periods under the US HSR Act and any other applicable legislation or
    regulations in any jurisdiction having expired or been terminated and there
    being no intimation of any intention to revoke or not to renew any of the
    same and all necessary statutory or regulatory obligations in any
    jurisdiction having been complied with;

(l) except as publicly announced by Aran prior to 17 August 1995, no member of
    the Wider Aran Group having, since 31 December 1994:

    (i)    save as between Aran and wholly owned subsidiaries of Aran or upon 
           the exercise of the right to subscribe for Aran shares pursuant to
           the exercise of options under any of the Aran share option schemes or
           pursuant to intra-group transactions on or prior to the date hereof,
           issued, authorised or proposed the issue of additional shares of any
           class;

    (ii)   save as between Aran and wholly owned subsidiaries of Aran, issued or
           authorised or proposed the issue of or granted securities convertible
           into, shares or rights, warrants or options to subscribe for, or
           acquire, any such shares or convertible securities;

    (iii)  save as between Aran and wholly owned subsidiaries of Aran, merged 
           with any body corporate or acquired or disposed of or transferred,
           mortgaged or charged or created any security interest over any assets
           or any rights, title or interest in any asset (including shares and
           trade investments) or authorised or proposed or announced any
           intention to propose any merger, demerger, acquisition, disposal,
           transfer, mortgage, charge or security interest other than in the
           ordinary course of business;

<PAGE>
 
                                     -10-
 
    (iv)   leased or in any other manner restricted or terminated its control 
           over or access to any of its material assets, whether for valuable
           consideration or otherwise, including (without limitation) by farm-
           out, of any of its right, title or interest under any licence or
           operating concession or other agreement concerning the exploration
           for, or the ownership, exploitation, extraction, development,
           production, operation or abandonment of, any oil, natural gas or
           other hydrocarbon deposit or reservoir or otherwise by granting
           rights to any person outside the Aran Group (or terminating any of
           its own rights) over or in relation to its oil, natural gas or other
           hydrocarbon interests or assets (whether or not in the ordinary
           course of its business);

    (v)    save as between Aran and wholly owned subsidiaries of Aran, 
           authorised or proposed or announced an intention to propose any
           change in its share or loan capital or to purchase any of its own
           shares;

    (vi)   save as between Aran and wholly owned subsidiaries of Aran, issued,
           authorised or proposed the issue of any debentures or incurred or
           increased any indebtedness or become subject to any contingent
           liability which is material in the context of the Wider Aran Group
           taken as a whole;

    (vii)  entered into any contract, reconstruction, amalgamation, commitment
           or other transaction or arrangement otherwise than in the ordinary
           course of business or entered into or changed the terms of any
           contract with any director or senior executive of any member of the
           Wider Aran Group;

    (viii) entered into any contract or commitment (whether in respect of 
           capital expenditure or otherwise) which is of a long term or unusual
           nature or which involves or could involve an obligation of a nature
           or magnitude in either case which is material in the context of the
           Wider Aran Group taken as a whole;

    (ix)   declared, paid, made or proposed to declare, pay or make, any bonus,
           dividend or other distribution;

    (x)    in the case of Aran, proposed any voluntary winding up;

    (xi)   waived any material claim; or

    (xii)  entered into any contract, commitment or agreement with respect to 
           any of the transactions or events referred to in this sub-paragraph
           (l) or announced any intention or passed any resolution to do so;

(m) since 31 December 1994 and save as disclosed in the accounts of Aran for the
    year then ended, (the "published results") or as publicly announced by Aran
    prior to 17 August 1995:

    (i)    no adverse change having occurred in the business, financial or 
           trading position or profits or assets or prospects of any member of
           the Wider Aran Group;

    (ii)   no contingent liability having arisen which would or might adversely
           affect any member of the Wider Aran Group; and

    (iii)  no litigation, arbitration proceedings, prosecution or other legal
           proceedings having been instituted or threatened by or against or
           remaining outstanding against any member of the Wider Aran Group
           which is adverse to and material in the context of the Wider Aran
           Group taken as a whole; and

(n) ARCO Irish Holdings not having discovered:

    (i)    that any financial or business information which has been publicly
           disclosed at any time by any member of the Aran Group either contains
           a misrepresentation of fact or omits to state a fact necessary to
           make the information contained therein not misleading, which
           misrepresentation or omission was not corrected by subsequent public
           announcement made on or before 17 August 1995 and is material in the
           context of the Offer; or

    (ii)   that any member of the Wider Aran Group which is not a subsidiary 
           of Aran is subject to any liability (contingent or otherwise) which
           is not disclosed in the published results and which has a material
           adverse effect on the Wider Aran Group taken as a whole.

In this Appendix 1 a reference to a "public announcement" by Aran shall mean an
announcement delivered by or on behalf of Aran to the Company Announcements
Office of the Irish Stock Exchange and the London Stock Exchange and publicly
announced shall be construed accordingly.

ARCO Irish Holdings reserves the right to waive (where possible), in whole or in
part, all or any of conditions (b) to (n) inclusive.  The Offer will lapse
unless all conditions relating to the Offer have been fulfilled or, if capable
of waiver, waived on or before 3.00 p.m. (Dublin and London time), 10.00 a.m.
(New York City time) on the first closing date (as defined below) or such later
date as ARCO Irish

<PAGE>
 
                                     -11-
 
Holdings may decide and in any event on or before midnight (Dublin and London
time), 7.00 p.m. (New York City time) on the sixtieth calendar day following
posting of the Offer document or on such later date as the Panel may agree. ARCO
Irish Holdings shall be under no obligation to waive or treat as satisfied any
of conditions (b) to (n) inclusive by a date earlier than the latest date
specified above for the satisfaction thereof notwithstanding that the other
conditions of the Offer may at such earlier date have been waived or fulfilled
and that there are at such earlier date no circumstances indicating that any
such conditions may not be capable of fulfilment. For the purpose of this
Appendix 1, the first closing date shall be the first calendar day following the
twentieth business day (as defined in the US Exchange Act) following posting of
the Offer document; if posting is on a business day, that day shall count as the
first day of such twenty business day period.

ARCO Irish Holdings intends, if appropriate, to seek the Panel's approval to
extend the date by which conditions (b) to (n) inclusive must be satisfied or
waived to not later than the eighty-first calendar day following posting of the
Offer document (or such later date as the Panel may agree).  Unless otherwise
determined by ARCO Irish Holdings (with the consent of the Panel), the Offer
will lapse unless at the latest time and date at which the Offer shall be
terminated or expire (the "closing date") condition (a) is or remains satisfied
by reference to acceptances and purchases permitted to be counted towards
fulfilling condition (a) (other than acceptances withdrawn on or before the
closing date), and subject to the consent of the Panel, by reference to the
issued share capital of Aran as at the first time and date on which condition
(a) is satisfied.

If ARCO Irish Holdings is required by the Panel to make an offer for Aran
securities under the provisions of Rule 9 of the City Code, ARCO Irish Holdings
may make such alterations to the conditions, including condition (a) above, as
are necessary to comply with the provisions of that Rule.

The Offer will lapse if the Acquisition is referred to the UK Monopolies and
Mergers Commission before 3.00 p.m.  (Dublin and London time), 10.00 a.m. (New
York City time) on the first closing date or the date on which the Offer becomes
or is declared unconditional as to acceptances, whichever is the later.

If the Minister for Enterprise and Employment of Ireland makes an order under
Section 9 of the Mergers Act prohibiting the Acquisition or prohibiting the
Acquisition except on conditions specified in such order, the Offer will lapse
unless, in the case of an order prohibiting the Acquisition except on conditions
specified in such order, ARCO Irish Holdings, in its absolute discretion, shall
decide to accept such conditions.

If the Offer lapses, the Offer will cease to be capable of further acceptance
and accepting Aran securityholders and ARCO Irish Holdings will cease to be
bound by Acceptance Forms submitted before the time when the Offer lapses.

<PAGE>
 
                                     -12-

                                  APPENDIX 2

                               BASES AND SOURCES

1.   The value of the issued share capital of Aran at the Offer price is based
     on 261,591,729 Aran shares (including Aran shares represented by Aran ADSs)
     in issue, as disclosed in the Extel card for Aran dated 17 August 1995.

2.   The last dealt price in Dublin of Aran shares on 18 August 1995 is derived
     from the Irish Stock Exchange Daily Official List.

3.   The share price high in Dublin of Aran for the last four years is derived
     from the Irish Stock Exchange Daily Official List.

4.   Applicable exchange rates as derived from the Financial Times dated 19
     August 1995:

          IR(Pounds)1 = Stg(Pounds)1.023
          IR(Pounds)1 = $1.5802

5.   Information on Aran is derived from Aran's annual report and accounts for
     the year ended 31 December 1994 and the annual report on Form 20-F filed
     with the SEC for the year ended 31 December 1994.

<PAGE>
 
                                     -13-
 
                                  APPENDIX 3

                        FINANCIAL EFFECTS OF ACCEPTANCE

CAPITAL VALUE

The following table shows, for illustrative purposes only and on the bases and
assumptions set out in the notes below, the financial effects of acceptance
of the Offer on capital value for a holder of 100 Aran shares, if the Offer
becomes or is declared unconditional in all respects.
<TABLE>
<CAPTION>
 
                                     Notes    IR(Pounds)   STG(Pounds) (ii)
<S>                                  <C>      <C>          <C>
Cash consideration                                60.00          61.38
Market value of 100 Aran shares      (iii)        42.50          43.48
                                              -----------------------------
Increase in capital value                         17.50          17.90
                                              -----------------------------
This represents an increase of                      41%            41%
</TABLE>
Notes:

(i)    No account has been taken of any potential liability to taxation.

(ii)   The Stg(Pounds) equivalent is based on the exchange rate set out in
       Appendix 2.

(iii)  The market value shown in the table for Aran shares is based on the 
       last dealt price in Dublin of IR42.5p per Aran share on 18 August 1995,
       being the last dealing day before the making of this announcement, as
       derived from the Irish Stock Exchange Official List.

<PAGE>
 
                                     -14-

                                  APPENDIX 4

                                  DEFINITIONS
 
"Acceptance Forms"              the Form of Acceptance and, with respect to
                                holders of Aran ADSs only, the Letter of
                                Transmittal and the Notice of Guaranteed 
                                Delivery

"Acquisition"                   the proposed acquisition by ARCO Irish Holdings
                                of all the Aran shares (including Aran shares
                                represented by Aran ADSs) pursuant to the Offer

"Aran ADSs"                     American Depositary Shares of Aran each
                                representing 30 Aran shares

"Aran"                          Aran Energy plc

"Aran Group"                    Aran and its subsidiary and associated
                                undertakings (as defined in the European
                                Communities (Group Accounts: Companies)
                                Regulations, 1992 of Ireland)

"Aran securities"               Aran shares and Aran ADSs

"Aran securityholders"          holders of Aran securities

"Aran shareholders"             holders of Aran shares

"Aran shares"                   the existing issued and fully paid ordinary
                                shares of IR20p each in Aran and any further
                                such shares unconditionally allotted or issued
                                while the Offer remains open for acceptance

"Aran share option scheme(s)"   any and all share option schemes operated by
                                Aran pursuant to which options to acquire Aran
                                shares have been or may be granted during the
                                pendency of the Offer

"ARCO"                          Atlantic Richfield Company

"ARCO Group"                    ARCO and its subsidiaries, ventures and
                                partnerships in which a controlling interest is
                                held, interests in undivided interest pipeline
                                companies and joint venture companies and its
                                equity interests in certain ventures and
                                partnerships in which less than a controlling
                                interest is held, as consolidated for accounting
                                purposes in the audited financial statements of
                                ARCO

"ARCO Irish Holdings"           ARCO Irish Holdings Inc.

<PAGE>
 
                                     -15-
 
"City Code"                     The City Code on Takeovers and Mergers in the UK

"Form of Acceptance"            the Form of Acceptance, authority and election
                                relating to the Offer

"IR(Pounds)"                    Irish pounds, being the lawful currency of the
                                Republic of Ireland

"IRp"                           Irish pence

"Ireland"                       Republic of Ireland

"Irish Companies Act"           the Companies Act, 1963 of the Republic of
                                Ireland, as amended

"Irish Stock Exchange"          the Irish Unit of the London Stock Exchange

"Letter of Transmittal"         the Letter of Transmittal relating to the Offer
                                for use by holders of Aran ADSs

"London Stock Exchange"         the International Stock Exchange of the United
                                Kingdom and the Republic of Ireland Limited

"NASDAQ"                        the electronic securities market operated by the
                                NASDAQ Stock Market, Inc.

"Notice of Guaranteed           the Notice of Guaranteed Delivery relating to
 Delivery"                      the Offer which may be used by holders of Aran
                                ADSs

"Offer"                         the cash offer to be made by Rothschilds on
                                behalf of ARCO Irish  Holdings to acquire all
                                the Aran shares including Aran shares
                                represented by Aran ADSs

"Panel"                         the Panel on Takeovers and Mergers in the UK

"Rothschilds"                   N M Rothschild & Sons Limited

"$"                             US dollars, being the lawful currency of the
                                United States of America

"SEC"                           US Securities and Exchange Commission

"Stg (Pounds)"                  pounds sterling, being the lawful currency of
                                the UK

"Stg p"                         UK pence

"UK" or "United Kingdom"        the United Kingdom of Great Britain and Northern
                                Ireland

<PAGE>
 
                                     -16-
 
"US" or "United States"         the United States of America, its possessions
                                and territories, all areas subject to its
                                jurisdiction or any subdivision thereof, any
                                State of the United States and the District of
                                Columbia

"US Exchange Act"               the US Securities Exchange Act of 1934, as
                                amended, and the rules and regulations
                                promulgated thereunder

"US HSR Act"                    the US Hart-Scott-Rodino Antitrust Improvements
                                Act of 1976, as amended

"Wider Aran Group"              Aran and any of its subsidiaries and any company
                                in which Aran has a substantial interest

<PAGE>
 
                                     -17-
 
                                  APPENDIX 5

                              INFORMATION ON ARCO


ARCO

ARCO is a Los Angeles-based energy company focused on hydrocarbons.  Worldwide
operations include all aspects of exploration, production and marketing of crude
oil, natural gas and natural gas liquids, as well as refining, marketing and
transportation of petroleum products.  ARCO mines and markets coal in the
Western US and Australia and has significant interests in two of America's
largest petrochemical companies.

ARCO's 1994 revenues were $17.2 billion; net income was $919 million; assets
totalled $24.6 billion; employees numbered approximately 23,000 at 31 December
1994.

ARCO is the fifth largest energy company in the US and in the top 50 largest US
industrial corporations as ranked by market value in the 1994 Fortune 500.

ARCO is the second largest oil producer in Alaska and operates the eastern half
of the Prudhoe Bay field on Alaska's North Slope, the nation's largest oilfield.
ARCO also operates Alaska's second and third largest oilfields - the Kuparuk
River and Point McIntyre fields - and is a 21.3 per cent. owner of the Trans
Alaska Pipeline System.

ARCO's 1994 worldwide oil and gas production was 900,000 barrels of crude oil
equivalent (BOE) per day.  Year end proven oil and gas reserves were 4  billion
BOE.

ARCO is the Number 1 marketer of gasoline on the West Coast with more than 1,500
branded retail outlets in five Western states - California, Oregon, Washington,
Arizona and Nevada.

ARCO is active in a number of international oil and gas projects, with major
exploration and development activities underway in Indonesia, the UK and China.
ARCO Chemical Company, in which ARCO has an 83.1 per cent. interest, is a world
leader in manufacturing and marketing its core products, including MTBE, styrene
monomer and propylene oxide.  ARCO also holds a 49.9 per cent. equity interest
in Lyondell Petrochemical Company, one of the largest and most efficient
petrochemical producers in the US.

<PAGE>
 
                                     -18-
 
ARCO IN THE UK

ARCO has been active in the UK since 1964, when it participated in the First
Licensing Round.  Since that time, the company has participated in approximately
100 exploration wells, of which 30 per cent. have resulted in discoveries.  ARCO
is currently the licence holder of 80 blocks, of which it operates 50.  In
addition to its active exploration programme, the company has also added
reserves through acquisitions, including the 1988 purchase of Tricentrol for
approximately $450 million.

First production started in 1968 with the East Leman gas field, followed in 1969
by additional production from the Hewett gas field.  In 1985, production levels
rose significantly as ARCO began producing from Thames, its first operated
field, as well as Balmoral and the V-fields.  Then in 1988, ARCO acquired
Tricentrol which contributed both existing production, new development projects
and new production over the next five years (Ravenspurn, Amethyst, Wytch Farm,
Thistle, Devron, Don, Osprey, Murdoch and Pickerill).  In 1994, ARCO's UK
operations produced approximately 23 MMBOE.  ARCO's UK operations are
predominately gas; in 1994, approximately three-quarters of total production
from the UK was gas.

Developments currently in progress include the Gawain gas field which is due on
stream in October of this year, as well as the Trent and Tyne gas fields, which
are expected to start up early in the fourth quarter of 1996.

ARCO's current UK Continental Shelf ("UKCS") proved reserves are approximately
230 MMBOE.  ARCO is the eighth largest gas producer in the UKCS, and the 12th
largest holder of oil and gas reserves in the UK.

ARCO's UK oil and gas operations have approximately 210 employees.


ARCO IN IRELAND

At present ARCO is a licence holder and operator of 10 whole or part blocks in
the Celtic Sea on which it has recently acquired a seismic survey.  This data is
now being processed and interpreted with the intent of developing exploration
prospects for drilling.

<PAGE>
 
                                     -19-
 
                                  APPENDIX 6

                              INFORMATION ON ARAN

This information and data is derived from Aran's 1994 Annual Report and its
Report on Form 20-F filed with the SEC for the year ended 31 December 1994.

Aran explores for, develops and produces oil and gas.  Aran's principal
activities are in the UK sector of the North Sea, the US Gulf Coast area and
offshore Ireland.

Aran is incorporated in Ireland.  Aran's shares are listed on the Irish Stock
Exchange and the London Stock Exchange, and its ADSs are quoted on NASDAQ.

Aran's primary producing assets include an approximate 14 per cent. working
interest in the Dunlin field, an approximate 5 per cent. working interest in the
Alba Field and an approximate 15 per cent. working interest in the Gryphon field
in the UK as well as interests in the South Pass 37 and East Potash fields in
the US.  Aran also has royalty interests in production from the Kinsale Head and
Ballycotton gas fields operated offshore Ireland.  Commercial reserves stand at
56 million barrels of oil equivalent with US proved SEC reserves of 42 million
barrels of oil equivalent.  Approximately 83 per cent. of Aran's reserves are
located in the UK with 15 per cent. in the US and 2 per cent. in Ireland.  Total
net production in 1994 was 15.1 thousand barrels equivalent per day.

Aran's exploration and appraisal drilling efforts are carried out in the UK
North Sea, US Gulf Coast, offshore Ireland and Turkey.  A recent exploration
success, the Schiehallion discovery, lies in the West of Shetlands area of the
UK North Sea.  Appraisal work is currently being carried out to assess the size
of the extension of the Schiehallion field into the acreage in which Aran has an
interest.

In Ireland, Aran holds a 100 per cent. interest in and is the operator of the
Connemara oilfield, located off the west coast of Ireland.  Aran participated in
the discovery well, which was drilled in 1979, but as at 31 December 1994 Aran
had not established a commercial development.

Aran is also engaged in the importation and sale of oil products in Ireland
through its 85 per cent. owned subsidiary, Estuary Fuel Ltd.  Fuel oil, gas oil,
petrol and other products are marketed in the south, south-west and west of
Ireland.  The minority interest in Estuary is owned by agricultural
cooperatives.

Aran's turnover in 1994 totalled IR(Pounds)83.4 million versus IR(Pounds)63.9
million in 1993.  After-tax profit in 1994 fell to IR(Pounds)3.7 million from
IR(Pounds)4.4 million in 1993.  At 31 December 1994, the company had total
assets of IR(Pounds)183.9 million and total liabilities of IR(Pounds)104.0
million, including IR(Pounds)67.3 million in long-term debt.

<PAGE>
 
                                     -20-
 
                                  APPENDIX 7

                              ARCO PRESS RELEASE

The following is the text of a press release issued by ARCO today.

"ARCO ANNOUNCES A CASH OFFER FOR ARAN

LOS ANGELES - ARCO (NYSE: ARC) announced today a cash offer to be made to
acquire any and all issued and to be issued shares of Aran Energy plc ("Aran"),
an independent oil and gas company incorporated in Ireland.

Aran has production in the UK North Sea, offshore Ireland, onshore and offshore
US Gulf of Mexico and participation in a possible discovery in the West of
Shetlands area, offshore UK.  Proved reserves at year-end 1994 were 42 million
barrels of oil equivalent (BOE).

The offer, which is 60 Irish pence per Aran share, values the issued share
capital of Aran at approximately $248 million.  (For each Aran American
Depositary Share, which represents 30 Aran shares, the offer is 18 Irish
pounds).

Aran shares are listed on the Irish and London Stock Exchanges.  Aran ADSs are
quoted on NASDAQ.

The offer, to be made by N M Rothschild & Sons Limited on behalf of ARCO Irish
Holdings Inc., ARCO's newly formed wholly owned subsidiary, represents:

 .  A premium of 41 per cent. over the last dealt price in Dublin of 42.5 Irish
   pence per Aran share on August 18, 1995, the last business day before this
   announcement;

 .  A premium of 28 per cent. over the Aran share price high in Dublin over the
   last four years of 47 Irish pence per share.

Announcing the offer, ARCO executive vice president William E Wade, Jr., said:
"ARCO is committed to expanding its operations internationally.  ARCO has been
active in Northwest Europe for more than 30 years and the proposed acquisition
of Aran fits ARCO's strategy of expanding its presence in this core region.

We believe our cash offer is a full and generous one.  We hope the Board of Aran
will recognise the merits of our offer and recommend acceptance of it as being
in the interests of Aran and its shareholders."

THE OFFER WILL BE SUBJECT TO THE TERMS AND CONDITIONS TO BE SET FORTH IN THE
FORMAL OFFER DOCUMENT.  THIS ANNOUNCEMENT DOES NOT CONSTITUTE AN INVITATION TO
PURCHASE ANY SECURITIES.

Note:  1 Irish pound = 1.023 sterling pounds and 1 Irish pound = $1.5802,
       derived from the Financial Times dated August 19, 1995."


<PAGE>
 
                                                              EXHIBIT 99.(a)(11)

                                 LOGO OF ARCO

                            Proposed Acquisition of
                                  ARAN ENERGY

                                    Dublin
                                August 21, 1995

<PAGE>
 
                                 LOGO OF ARCO

                            Proposed Acquisition of
                                  ARAN ENERGY

                                    London
                                August 21, 1995

<PAGE>
 
                                   ARCO Team

Dublin
 . Bill Wade


 . Jay Cheatham


London
 . Terry Dallas
<PAGE>
 
                              The ARCO Cash Offer


 . 60 Irish pence per share (61.4p)

 . Values Aran at IR(Pound)157 million ((Pound)161 million)


<PAGE>
 
                              Background on ARCO

 . One of the world's leading integrated oil and gas companies

 . Headquarters in Los Angeles, California

 . Major operations in the US, UK, the Netherlands, Indonesia and Australia

 . In addition to Ireland, also active in 15 other countries around the world

 . Operations include
  - Exploration, production and marketing of crude oil, natural gas and natural 
    gas liquids
  - Refining, marketing and transportation of petroleum products
  - Mining and marketing coal
  - Interests in two petrochemical companies

 . Over 125 years of active experience in petroleum related industries
<PAGE>
 
                         Major Worldwide Oil Companies

                     Market Capitalisation ($Bn) (Equity)

                     Bar Chart with plot points identified

         Royal Dutch Shell                                     101
         Exxon                                                  86
         BP                                                     49
         Mobil                                                  38
         Amoco                                                  31
         Chevron                                                31
         Elf                                                    20
         ARCO                                                   18
         Texaco                                                 17
         Total                                                  14
         Phillips                                                9
         Occidental                                              7
         Unocal                                                  7
         YPF                                                     6

                                                  Source: Bloomberg, Aug 18 1995

<PAGE>
 
                               ARCO 1994 Results


After-tax net income                      $920 million

Total revenues                            $17 billion

Total year-end assets                     $25 billion

Year-end proved oil and gas reserves      4 billion barrels oil equivalent (BOE)

Total oil and gas production              900 thousand BOE per day

Refinery crude runs                       400 thousand barrels per day

Coal shipments                            50 million tons


                                                      Source: 1994 Annual Report
<PAGE>
 
                            ARCO Reserve Portfolio

                                          
               1987                                        1994            
                                                                       
      PIE CHART APPEARS HERE                      PIE CHART APPEARS HERE  

      International       9%                      International      21%
      Continental U.S.   31%                      Continental U.S.   27%
      Alaska             60%                      Alaska             52% 

                                            *Proved reserves from Annual Reports
<PAGE>
 
                            Global Exploration and
                             Production Activities

                         MAP OF THE WORLD APPEARS HERE

The following locations are identified on the map: Alaska, United States, 
Trinidad & Tobago, Venezuela, Ecuador, Peru, Ireland, United Kingdom, 
Netherlands, Romania, Turkey, Tunisia, Algeria, Egypt, Gabon, Congo, Qatar, 
Dubai, Yemen, China, Myanmar, Vietnam, Philippines, and Indonesia.

<PAGE>
 
                                ARCO in Ireland

 . Active in oil and gas exploration since 1985

 . Cumulative expenditure of over $14 million on oil and gas exploration

 . Currently licence holder and operator on 10 whole or part blocks in the Celtic
  Sea

 . Processing seismic data on these blocks with a view to selecting prospects for
  drilling
<PAGE>
 
                                ARCO in the UK

 . Active in UK since 1964

 . 210 employees

 . Current licence holder on 80 whole or part blocks; operator of 50

 . Participated in approximately 100 exploration wells with 30% success rate

 . 230 million BOE proved reserves
  450 million BOE proved and potential reserves

 . 1994 production approximately 63,000 BOE/day

 . $1.9 billion invested in exploration and development activities

 . Active developments as operator on Gawain, Trent and Tyne
<PAGE>
 
                                 Licence
                               Interests

                                                  GRAPHIC APPEARS HERE

A map of Ireland and surrounding seas with various licence interests identified 
as ARCO, Aran, Celtic Sea Royalty or Joint operations (205/26a). The licence 
interest blocks in the surrounding seas are identified by number. The following 
oil fields are identified by name: Alba, Gryphon, Dunlin and Schiehallion. The 
Connemaka oil find is also identified on the map.
<PAGE>
 
                           ARCO'S Strategy for Aran

Apply ARCO's technical and financial strengths to Aran's portfolio of assets

 . Producing fields

 . West of Shetlands

 . Connemara

 . North Sea and Irish acreage
<PAGE>
 
                                   The Offer

 . ARCO offering 60 Irish pence per share (61.4p)

 . A cash offering valuing Aran at IR(Pounds)157 million ((Pounds)161 million)

 . 41% above the price on Friday 18 August, the last trading day before the offer
  was announced

 . 28% above the share price high of the last four years

 . Aran has never paid a dividend; the offer provides Aran shareholders with a
  means of generating income on their capital

 . "ARCO believes the cash offer is full and generous"

<PAGE>

                                                              EXHIBIT 99.(a)(12)

                       LETTERHEAD OF FINANCIAL DYNAMICS

                           Financial Communications
 

 
Date:     25th August 1995                            FOR  IMMEDIATE RELEASE


Contact:   BRIAN BELL - WHPR (353) 1 496 0244
           NICK MILES/MARC POPIOLEK - Financial Dynamics (44) 171 831 3113
 


           NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO 
                          AUSTRALIA, CANADA OR JAPAN


                            ARCO IRISH HOLDINGS INC.
                            ("ARCO IRISH HOLDINGS")
                          A WHOLLY OWNED SUBSIDIARY OF
                           ATLANTIC RICHFIELD COMPANY
                                    ("ARCO")
                       IR (Pounds)157 MILLION CASH OFFER
                                      FOR
                                ARAN ENERGY PLC
                                    ("ARAN")



The Offer Document for the cash offer made by N M Rothschild & Sons Limited on
behalf of ARCO Irish Holdings to acquire the whole of Aran's issued (and to be
issued) share capital is being posted today.

The Offer Document includes the following letter addressed to holders of Aran
shares and Aran ADSs from Bill Wade, Chairman of ARCO Irish Holdings:

"On 21 August 1995, the Board of ARCO Irish Holdings announced the terms of a
cash offer for all of Aran's issued and to be issued share capital (including
Aran shares represented by Aran ADSs) at IR60p per share (and IR(Pounds)18.00
per Aran ADS).

ARCO is one of the world's leading integrated oil and gas companies, with
corporate headquarters in Los Angeles, California.  ARCO and its affiliates have
major operations in the US, the UK, the Netherlands, Indonesia and Australia.
In addition, ARCO has exploration and production operations in 16 other
countries including Ireland.  ARCO and its affiliates employ approximately
23,000 people worldwide.

ARCO has been active in the UK North Sea and in the waters surrounding Ireland
since 1964 and 1985, respectively.  In the UK, ARCO has actively participated
since the first license round with $1.9 billion invested in exploration and
development 
<PAGE>
 
activities, and has been involved in exploration activities on 16 Irish blocks
with expenditure in Ireland of over $14 million.

Historically, ARCO's producing assets were predominantly US based.  For a number
of years, ARCO has pursued a strategy of expanding globally its exploration and
production operations.  The acquisition of Aran, which would add complementary
assets in the core area of Northwest Europe, is a positive step in support of
this strategy.

The Offer represents full and generous value for all of Aran's assets, including
its:

 . core producing assets, the Alba and Gryphon oil fields, where values were
  indicated in recent auction sales of interests in those fields;

 . 17.65% interest in block 204/25a, which holds an undetermined unit interest
  in the Schiehallion oil field, where the reserves and the cost of development
  have not yet been defined publicly and must be judged against the inherent
  risks associated with a project at this stage of its development in the new
  and exposed West of Shetlands area; and

 . 100% interest in the Connemara oil find, discovered by BP in 1979 but
  subsequently relinquished by BP in 1989, for which considerable appraisal work
  still needs to be done before commerciality can be determined.

ARCO has both the financial and technical resources to carry the risk and
exploit these assets successfully.

We believe our Offer is full and fair.  We strongly urge you to accept it."


                                    - ENDS -

<PAGE>
 
                                                              EXHIBIT 99(a)(13)

This announcement is neither an offer to purchase nor a solicitation of an
offer to purchase securities. The Offer is made in the United States solely by
the Offer Document dated August 25, 1995, the Letter of Transmittal, the Form
of Acceptance and related materials and is not being made to, nor will the
Offer be accepted from or on behalf of, holders of Aran shares or Aran ADSs in
any jurisdiction in which the making or acceptance thereof would not be in
compliance with the laws of such jurisdictions. In those US jurisdictions whose
securities laws or blue sky laws require the Offer to be made by a licensed
broker or dealer, the Offer shall be deemed to be made on behalf of ARCO Irish
Holdings Inc. by Rothschild Inc. or one or more registered brokers or dealers
which are licensed under the laws of those jurisdictions. The Offer Document,
the Letter of Transmittal, the Form of Acceptance and related materials should
not be forwarded or transmitted in or into Australia, Canada or Japan.

                              Notice of Offer by
                         N M Rothschild & Sons Limited
                                 on behalf of
                           ARCO Irish Holdings Inc.
                         a wholly owned subsidiary of
                          Atlantic Richfield Company
                          to acquire all outstanding
                Ordinary Shares and American Depositary Shares
                                      of
                                ARAN ENERGY PLC

    N M Rothschild & Sons Limited, acting in the United States through
Rothschild Inc., on behalf of ARCO Irish Holdings Inc. ("ARCO Irish Holdings"),
is offering to purchase, upon the terms and subject to the conditions set forth
in the offer document dated August 25, 1995 (the "Offer Document"), the related
Letter of Transmittal and the related Form of Acceptance (collectively, the
"Offer"), (i) all outstanding fully paid ordinary shares of IR20p each ("Aran
shares") of Aran Energy plc ("Aran") for IR60p per Aran share in cash and (ii)
all outstanding Aran American Depositary Shares, each representing thirty Aran
shares ("Aran ADSs") and evidenced by Aran American Depositary Receipts ("Aran
ADRs"), for IR Pound 18.00 per Aran ADS in cash.

     Aran shares and Aran ADSs (evidenced by Aran ADRs) are referred to
collectively as "Aran securities" and holders of Aran securities are referred
to as "Aran securityholders". The Offer will extend to any Aran securities
unconditionally allotted or issued fully paid prior to the date on which the
Offer becomes or is declared unconditional (or such later date as ARCO Irish
Holdings may decide) pursuant to the exercise of options granted under Aran
share option scheme(s) (as discussed in the Offer Document). ARCO Irish
Holdings' obligation to purchase Aran securities pursuant to the Offer is
subject to certain conditions as set forth in the Offer Document. ARCO Irish
Holdings is a wholly owned subsidiary of Atlantic Richfield Company ("ARCO")
and both ARCO and ARCO Irish Holdings are Delaware corporations. Aran is
incorporated in the Republic of Ireland. Terms used herein and not otherwise
defined shall have the respective meanings assigned to them in the Offer
Document and all amounts shown herein are in Irish pounds.

THE OFFER IS OPEN FOR ACCEPTANCE UNTIL 3:00 P.M. (DUBLIN AND LONDON TIME),
10:00 A.M. (NEW YORK CITY TIME), ON SEPTEMBER 23, 1995 (THE "INITIAL PERIOD"),
UNLESS EXTENDED (IN ACCORDANCE WITH THE TERMS THEREOF). AT THE CONCLUSION OF
THE INITIAL PERIOD OR ON OR BEFORE THE CONCLUSION OF ANY EXTENSION THEREOF AND
ON THE SATISFACTION OR, WHERE PERMITTED, WAIVER OF THE CONDITION(S) TO THE
OFFER, THE PURCHASE OF ALL ARAN SECURITIES IN RESPECT OF WHICH THE OFFER HAS
BEEN VALIDLY ACCEPTED AND NOT WITHDRAWN WILL TAKE PLACE, AND THE OFFER WILL BE
EXTENDED FOR A SUBSEQUENT PERIOD OF AT LEAST FOURTEEN CALENDAR DAYS. PRIOR TO
THE OFFER BECOMING OR OTHERWISE BEING DECLARED UNCONDITIONAL IN ALL RESPECTS,
ACCEPTING ARAN SECURITYHOLDERS WILL HAVE THE RIGHT TO WITHDRAW THEIR
ACCEPTANCES IN RESPECT THEREOF. HOWEVER, IN THE EVENT OF THE OFFER BECOMING OR
BEING DECLARED UNCONDITIONAL IN ALL RESPECTS, NO RIGHTS OF WITHDRAWAL WILL BE
AVAILABLE TO ACCEPTING ARAN SECURITYHOLDERS IN THE SUBSEQUENT PERIOD DURING
WHICH THE OFFER REMAINS OPEN FOR ACCEPTANCE.

     The Offer is conditional, inter alia, on valid acceptances being received
in respect of not less than 95% of the Aran shares (including Aran shares
represented by Aran ADSs) to which the Offer relates, or such lesser percentage
as ARCO Irish Holdings may decide provided that this condition shall not be
satisfied unless ARCO Irish Holdings and/or its wholly owned subsidiaries shall
have acquired or agreed to acquire, pursuant to the Offer or otherwise, Aran
shares (including Aran shares represented by Aran ADSs) carrying more than 50
percent of the voting rights normally exercisable at general meetings of Aran.

     If, as a result of the Offer and subject to certain conditions, ARCO Irish
Holdings receives acceptances of the Offer in respect of Aran shares (including
Aran shares represented by Aran ADSs) representing at least 80% in value of the
Aran shares (including Aran shares represented by Aran ADSs) to which the Offer
relates, then provided such requirement is achieved within four months of
August 25, 1995, ARCO Irish Holdings will be entitled and intends to effect the
compulsory acquisition procedures provided for in Section 204 of the Irish
Companies Act, 1963 of the Republic of Ireland, as amended, to compel the
purchase of any outstanding Aran shares (including Aran shares represented by
Aran ADSs) not acquired pursuant to the Offer or otherwise, on the terms of the
Offer, in accordance with relevant procedures and time limits described in
Section 204 of such Act.

     ARCO Irish Holdings expressly reserves the right (but will not be
obligated) at any time, and from time to time, to extend the Initial Period,
and, in such event, will make a public announcement of such extension and give
oral or written notice of such extension to First Chicago Trust Company of New
York, the US Depositary for the Offer, AIB Bank, the Irish Receiving Agent for
the Offer, and The Royal Bank of Scotland plc, the UK Receiving Agent for the
Offer. During any such extension, all Aran securities in respect of which the
Offer has been accepted and not withdrawn will remain subject to the Offer,
subject to the right of a holder who has accepted the Offer to withdraw such
Aran securities during the Initial Period as so extended. If all the conditions
have not been satisfied or, where permitted, waived prior to midnight (Dublin
and London time), 8:00 p.m. (New York City time), on October 24, 1995, the Offer
will lapse in the absence of a competitive bid and/or unless otherwise agreed by
the Panel on Takeovers and Mergers of the UK (the "Panel").

     The consideration for Aran securities accepted for purchase pursuant to the
Offer will be paid within 21 calendar days of the Offer becoming or being
declared unconditional in all respects or, if later, the receipt of a complete
and valid Letter of Transmittal with respect to Aran ADSs or Form of Acceptance
with respect to Aran shares, together with other required documentation in
accordance with the terms of the Offer Document and the Letter of Transmittal
or Form of Acceptance, as the case may be. Although the Offer is denominated in
Irish pounds, accepting Aran securityholders will be entitled to receive their
cash consideration in pounds sterling or US dollars at prevailing exchange
rates on the latest practicable business day preceding the date of payment.

     If a holder of Aran ADSs wishes to accept the Offer in respect of Aran ADSs
and the Aran ADRs evidencing such Aran ADSs are not immediately available or
the procedures for book-entry transfer cannot be completed on a timely basis,
or if time will not permit all required documents to reach the US Depositary
prior to the expiry of the Offer, such holder's acceptance of the Offer in
respect of Aran ADSs may nevertheless be effected by following the guaranteed
delivery procedures set forth in the Offer Document.

     Although no revision is envisaged, if the Offer (in its original or any
previously revised form) is revised and any such revision represents, on the
date on which such revision is announced (on such basis as N M Rothschild &
Sons Limited may consider appropriate), an improvement (or no diminution) in
the value of the consideration under the Offer as so revised compared with the
value of the total consideration previously offered, the Letter of Transmittal
and Form of Acceptance authorize ARCO Irish Holdings and N M Rothschild & Sons
Limited to accept the Offer as so revised on behalf of Aran securityholders who
have previously accepted the Offer, subject to the rights of such Aran
securityholders to revoke such authority as described in the Offer Document.

     Except as otherwise provided in the Offer Document, acceptances of the
Offer for Aran securities are irrevocable. Acceptances of the Offer may be
withdrawn pursuant to the procedures set out below at any time prior to the
Offer becoming unconditional (whether in accordance with its terms or by
revision or waiver of its conditions), which in any event will not be prior to
the end of the Initial Period or any extension thereof (in accordance with the
terms thereof). Acceptances of the Offer in respect of Aran securities received
during the Initial Period (or any extension thereof) and not withdrawn prior to
the end of the Initial Period (or any extension thereof) and acceptances of the
Offer in respect of Aran securities received subsequent to the end of the
Initial Period (or any extension thereof) may not be withdrawn. ARCO Irish
Holdings may terminate any extension (other than an extension required by the
City Code or by the US federal securities laws or the rules and regulations
thereunder) of the Initial Period prior to its scheduled conclusion if all
conditions to the Offer are satisfied or, where permitted, waived. In such event
the Initial Period and, consequently, withdrawal rights will terminate
immediately.

     To be effective, a written notice of withdrawal (or, in respect of tenders
made pursuant to a Letter of Transmittal only, a facsimile transmission
thereof) must be timely received by the party (either the Irish Receiving
Agent, the UK Receiving Agent or the US Depositary) to whom the Acceptance Form
was originally sent at one of the addresses set forth in the Offer Document and
must specify the name of the person whose acceptance is to be withdrawn, the
number of Aran ADSs and/or Aran shares to be withdrawn and (if an Aran share
certificate or Aran ADR has been delivered) the name of the registered holder
of the Aran securities, if different from the name of the person whose
acceptance is to be withdrawn. In respect of Aran ADRs, if Aran ADRs have been
delivered or otherwise identified to the US Depositary then, prior to the
physical release of such Aran ADRs, the serial numbers shown on such Aran ADRs
must be submitted and, unless the Aran ADSs evidenced by such Aran ADRs have
been delivered by an Eligible Institution or the Offer accepted by means of a
Letter of Transmittal, the signatures on the notice of withdrawal must be
guaranteed by an Eligible Institution. If Aran ADSs have been delivered
pursuant to the procedures for book-entry transfer set forth in the Offer
Document, any notice of withdrawal must also specify the name and number of
account at the appropriate Book-Entry Transfer Facility to be credited with the
withdrawn Aran ADSs and must otherwise comply with such Book-Entry Transfer
Facility's procedures.

     All questions as to the withdrawal will be determined by ARCO Irish
Holdings, whose determination (except as required by the Panel) shall be final
and binding. None of ARCO Irish Holdings, N M Rothschild & Sons Limited, the
Irish Receiving Agent, the UK Receiving Agent, the US Depositary, the US Dealer
Manager, or any other person will be under any duty to give notification of any
defects or irregularities in any notice of withdrawal or incur any liability for
failure to give any such notification.

     The Offer Document and related materials contain important information
which should be read carefully before any decisions are made with respect to the
Offer. The Offer Document and the Acceptance Forms are being mailed to holders
of record of Aran shares and Aran ADSs and are being furnished to brokers,
dealers, commercial banks, trust companies and similar persons, whose names or
the names of whose nominees appear as holders of record for subsequent
transmittal to beneficial owners of Aran securities.

     The information required to be disclosed by Rule 14d-6(e)(1)(vii) of the
General Rules and Regulations under the US Securities Exchange Act of 1934, as
amended, is contained in the Offer Document and incorporated herein by
reference.

     Requests for assistance or copies of the Offer Document, the Letter of
Transmittal, the Notice of Guaranteed Delivery and the Form of Acceptance may
be directed to the US Depositary at the addresses and telephone numbers set
forth below or to the Irish Receiving Agent or UK Receiving Agent at the
addresses and telephone numbers set forth in the Offer Document, and copies
will be furnished promptly at ARCO Irish Holdings's expense.

                      The US Depositary for the Offer is:

                    FIRST CHICAGO TRUST COMPANY OF NEW YORK
                                  Suite 4680
                                14 Wall Street
                                 Eighth Floor
                           New York, New York 10005

      Facsimile Copy Number:                     For Information Call:
      
      (201) 222-4720 or 4721                   (800) 659-6111 (Toll Free)
       Confirm by Telephone:                        or (201) 324-0137
         (201) 422-4707  

             By Mail:                         By Hand or Overnight Courier:
           Suite 4660                                 Suite 4680
         P.O. Box 2559                              14 Wall Street
     Jersey City, NJ 07303                            Eighth Floor
                                                  New York, NY 10005

           The Dealer Manager for the Offer in the United States is:

                                ROTHSCHILD INC.
                          1251 Avenue of the Americas
                                  51st Floor
                              New York, NY 10020
                      (212) 403-3611 within New York City
          (800) 753-5151 ext. 3611 (Toll Free) outside New York City

August 25, 1995

<PAGE>
 
                                                           EXHIBIT EX-99.(a)(14)

                                   Offer by
                         N M Rothschild & Sons Limited
                                 on behalf of
                           ARCO Irish Holdings Inc.
                                      for
                                Aran Energy plc

                              -------------------

N M Rothschild & Sons Limited ("Rothschilds") on behalf of ARCO Irish Holdings 
Inc. announces an Offer to acquire the entire issued and to be issued ordinary 
share capital of Aran Energy plc (including such shares represented by American
Depositary Shares) on the terms of an Offer Document issued today. Copies of the
Offer Document, acceptance forms and other relevant documents may be obtained by
holders of such shares and ADSs from:

N M Rothschild & Sons Limited
New Court
St. Swithin's Lane
London EC4P 4DU

This advertisement is published on behalf of ARCO Irish Holdings Inc. and has 
been approved by Rothschilds, which is regulated in the UK by The Securities and
Futures Authority Limited, solely for the purposes of Section 57 of the 
Financial Services Act 1986.

Rothschilds is acting for Atlantic Richfield Company ("ARCO") and ARCO Irish 
Holdings Inc. and no one else in connection with the Offer and will not be 
responsible to anyone other than ARCO and ARCO Irish Holdings Inc. for providing
the protections afforded to the customers of Rothschilds or for providing advice
in relation to the Offer. Rothschilds is acting through Rothschild Inc. for the 
purpose of making the offer in the United States.

The Directors of ARCO Irish Holdings Inc. and the bid committee of ARCO accept 
responsibility for the information contained in this advertisement. To the best 
of their knowledge and belief (having taken all reasonable care to ensure that 
such is the case), the information contained in this advertisement is in 
accordance with the facts and does not omit anything likely to affect the import
of such information.

                                                                 August 25, 1995

<PAGE>

                                                              EXHIBIT 99.(a)(15)

                              SUBSTITUTE FORM W-9
 
  THE INFORMATION IN THIS DOCUMENT IS RELEVANT ONLY TO HOLDERS OF ARAN SHARES
WHO SEND THE FORM OF ACCEPTANCE, AUTHORITY AND ELECTION TO FIRST CHICAGO TRUST
                              COMPANY OF NEW YORK
 
   SUBSTITUTE FORM W-9 AND 31% U.S. BACK-UP WITHHOLDING. In order to avoid
"back-up withholding" of U.S. Federal income tax on any cash payment received
upon the surrender of Aran shares to First Chicago Trust Company of New York
(the "US Depositary") pursuant to the Offer, an Aran shareholder must, unless
an exemption applies, provide the US Depositary with his correct Taxpayer
Identification Number ("TIN") on Substitute Form W-9 and certify, under
penalties of perjury, that such number is correct and that he is not subject
to back-up withholding. If the correct TIN is not provided a $50 penalty may
be imposed by the Internal Revenue Service and cash payments made in exchange
for the surrendered Aran shares may be subject to back-up withholding of 31%.
 
   Back-up withholding is not an additional U.S. Federal income tax. Rather,
the U.S. Federal income tax liability of persons subject to back-up
withholding will be reduced by the amount of such tax withheld. If back-up
withholding results in an overpayment of taxes, a refund may be applied for
from the Internal Revenue Service.
 
   The TIN that is to be provided on the Substitute Form W-9 is that of the
registered holder(s) of the Aran shares or of the last transferee appearing on
the transfers attached to, or endorsed on, the Aran shares. The TIN for an
individual is his social security number. The box in Part 2 of the Substitute
Form W-9 may be checked, if the person surrendering the Aran shares has not
been issued a TIN and has applied for a TIN or intends to apply for a TIN in
the near future. If the box in Part 2 is checked, the person surrendering the
Aran shares must also complete the Certificate of Awaiting Taxpayer
Identification Number below. Notwithstanding that the box in Part 2 is checked
(and the Certificate of Awaiting Taxpayer Identification Number is completed),
the US Depositary will withhold 31% on any cash payment of the purchase price
for the Aran shares made prior to the time it is provided with a properly
certified TIN.
 
   Exempt persons (including among others, corporations) are not subject to
back-up withholding. A foreign individual or foreign entity may qualify as an
exempt person by submitting a statement (on Form W-8), signed under penalties
of perjury, certifying such person's foreign status. Form W-8 can be obtained
from the US Depositary. An Aran shareholder should consult his tax advisor as
to his qualification for an exemption from back-up withholding and the
procedure for obtaining such exemption.
 
   For additional guidance, see the enclosed Guidelines for Certification of
Taxpayer Identification Number on Substitute Form W-9.
<PAGE>
 
--------------------------------------------------------------------------------
                     PART 1 - PLEASE PROVIDE YOUR TIN
                     IN THE BOX AT RIGHT AND CERTIFY
                     BY SIGNING AND DATING BELOW
                      
 
 
                   ------------------------------------ 
                     CERTIFICATION - UNDER THE           Social Security Number
                     PENALTIES OF PERJURY, I CERTIFY     or Employer
                     THAT:                               Identification Number
    
                     1. The number shown on this form    ---------------------
                        is my correct taxpayer         
                        identification number (or I am 
                        waiting for a number to be     
                        issued to me), and              
                                    
                     2. I am not subject to back-up    
                        withholding because (a) I am                          
                        exempt from back-up                                   
                        withholding or (b) I have not                         
                        been notified by the Internal                         
                        Revenue Service ("IRS") that I                        
                        am subject to back-up                                 
                        withholding as a result of a                          
                        failure to report all interest                        
                        or dividends, or (c) the IRS                          
                        has notified me that I am no                          
                        longer subject to back-up                             
                        withholding.                          
                                                               
                    
                    ------------------------------------
   SUBSTITUTE        Certification Instructions - you
   Form W-9          must cross out item 2 above if
   Department of     you have been notified by the IRS
   the Treasury      that you are currently subject to
   Internal          back-up withholding because of
   Revenue           underreporting interest or
   Service           dividends on your tax return.
                     
                     NAME .............................
                               (Please Print)
  
                     ADDRESS ..........................
   Payer's           
   Request for       ..................................
   Taxpayer                  (include Zip Code)
   Identification                                                  Part 2     
   Number (TIN)      SIGNATURE ..........DATE .........       [_]Awaiting TIN 
                    
--------------------------------------------------------------------------------
 
 YOU MUST COMPLETE THE FOLLOWING CERTIFICATION IF YOU CHECKED THE BOX IN PART 2
                                       OF
                              SUBSTITUTE FORM W-9

--------------------------------------------------------------------------------
             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

I certify under penalties of perjury that a taxpayer identification number has
not been issued to me, and either (a) I have mailed or delivered an application
to receive a taxpayer identification number to the appropriate Internal Revenue
Service Center or Social Security Administration Office or (b) I intend to mail
or deliver an application in the near future. I understand that, notwithstanding
that I have checked the box in Part 2 (and have completed this Certificate of
Awaiting Taxpayer Identification Number), all reportable payments made to me
prior to the time I provide the US Depositary with a properly certified taxpayer
identification number will be subject to a 31% back-up withholding tax.

   Signature ................................     Date ....................

--------------------------------------------------------------------------------

NOTE: FAILURE TO COMPLETE AND RETURN THIS SUBSTITUTE FORM W-9 MAY RESULT IN 
      BACK-UP WITHHOLDING OF 31% OF ANY CASH PAYMENT MADE TO YOU. PLEASE REVIEW
      THE ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
      NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS

 
                      The US Depositary for the Offer is:
 
                         First Chicago Trust Company of
                                    New York
                      Call: (800) 659-6111 (Toll Free) or
                                 (201) 324 0137
 
   Tenders & Exchanges                                Tenders & Exchanges
   Suite 4680-ARN                                              Suite 4660
   14 Wall Street                                       P.O. Box 2559-ARN
   8th Floor                                      Jersey City, New Jersey
   New York, New York                                          07303-2559
   10005
 
                    The US Dealer Manager for the Offer is:
 
                                Rothschild Inc.
                          1251 Avenue of The Americas
                                   51st Floor
                               New York, NY 10020
 
                 (212) 403-3611 (Collect) within New York City
           (800) 753-5151 ext. 3611 (Toll Free) outside New York City


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