BP AMOCO PLC
SC 13D, 1999-04-12
PETROLEUM REFINING
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                       SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549


                                  SCHEDULE 13D
                                 (Rule 13d-101)
                    Under the Securities Exchange Act of 1934
       INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO 13d-1(a)
                AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2(a)


                           Atlantic Richfield Company
- - --------------------------------------------------------------------------------
                                (Name of Issuer)


                    Common Stock (par value $2.50 per share)
- - --------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                    04882510
                               -----------------
                                 (CUSIP Number)


                                Peter B.P. Bevan
                                 BP Amoco p.l.c.
                                 Britannic House
                                1 Finsbury Circus
                                 London EC2M 7BA
                                (44) 171-596-4000

                  ---------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)


                                 March 31, 1999
                           ---------------------------

             (Date of Event Which Requires Filing of This Statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box [ ].

NOTE:  Six copies of this statement, including all exhibits, should be filed
with the Commission.  See Rule 13d-1(a) for other parties to whom copies are to
be sent.


                                       -1-

<PAGE>


- - --------------------
CUSIP NO. 04882510
- - --------------------
- - ---------------------------------------
 1.      NAME OF REPORTING PERSON
         I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)

         BP Amoco p.l.c.; I.R.S. Identification No.: None
- - ---------------------------------------
 2.      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                             (a)  [  ]

                                                             (b)  [  ]
- - ---------------------------------------
 3.      SEC USE ONLY

- - ---------------------------------------
 4.      SOURCE OF FUNDS

         WC
- - ---------------------------------------
 5.      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS
         REQUIRED PURSUANT TO ITEMS 2(D) OR 2(E)
                                                                  [  ]
- - ---------------------------------------
 6.      CITIZENSHIP OR PLACE OF ORGANIZATION

         England and Wales
- - ---------------------------------------
                           7.       SOLE VOTING POWER
  NUMBER OF                         64,861,617*
     SHARES                ----------------------------------------
BENEFICIALLY               8.       SHARED VOTING POWER
  OWNED BY                          0
       EACH                ----------------------------------------
  REPORTING                9.       SOLE DISPOSITIVE POWER
     PERSON                         64,861,617*
       WITH                ----------------------------------------
                           10.      SHARED DISPOSITIVE POWER
                                    0
                           ----------------------------------------



                                       -2-

<PAGE>



11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING
         PERSON

         64,861,617*
- - ------------------------------------------------------------
12.      CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
         CERTAIN SHARES

                                                     |-|
- - ------------------------------------------------------------
13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

         19.9%
- - ------------------------------------------------------------
14.      TYPE OF REPORTING PERSON

         CO
- - ------------------------------------------------------------

- - --------
*         The shares of common stock, par value $2.50 per share ("ARCO Common
          Shares"), of Atlantic Richfield Company ("ARCO") covered by this item
          are purchasable by BP Amoco p.l.c. ("BP Amoco") upon exercise of an
          option granted to BP Amoco on March 31, 1999, and described in Item 4
          of this Statement. The number of shares subject to the option may be
          adjusted, as described in Item 4. Prior to the exercise of the option,
          BP Amoco is not entitled to any rights as a shareholder of ARCO as to
          the ARCO Common Shares covered by the option. The option may be only
          exercised upon the happening of certain events referred to in Item 4,
          none of which has occurred as of the date hereof. BP Amoco disclaims
          any beneficial ownership of the ARCO Common Shares which are
          purchasable by BP Amoco upon exercise of the option, because the
          option is exercisable only in the circumstances referred to in Item 4
          below, none of which has occurred as of this date. If the option were
          exercised, BP Amoco would have the sole right to vote or to dispose of
          the ARCO Common Shares issued as a result of such exercise.


                                       -3-


<PAGE>


                                  SCHEDULE 13D
                         RELATING TO THE COMMON SHARE OF
                           ATLANTIC RICHFIELD COMPANY

Item 1.   Security and Issuer.
          -------------------

          This Statement on Schedule 13D (this "Statement") relates to the
common share, par value $2.50 per share (each, an "ARCO Common Share"), of
Atlantic Richfield Company, a Delaware corporation ("ARCO"). The principal
executive offices of ARCO are located at 333 South Hope Street, Los Angeles,
California 90071.

Item 2.   Identity and Background.
          ----------------------

          This Statement is being filed by BP Amoco p.l.c., an English public
limited company ("BP Amoco"). The principal business address of BP Amoco is
Britannic House, 1 Finsbury Circus, London, EC2M 7BA, England. BP Amoco is a
company operating in the petroleum and petrochemical industries.

          (a)-(c); (f)  The name, business address, present principal occupation
or employment, and the name and principal business of any corporation or other
organization in which such employment is conducted of each of the directors and
executive officers of BP Amoco is set forth in Schedule I hereto. Except as
otherwise indicated in Schedule I, each person listed in Schedule I hereto is a
citizen of the United Kingdom.

          (d)-(e)  During the last five years, neither BP Amoco nor, to the
knowledge of BP Amoco, any of the persons listed on Schedule I hereto, (i) has
been convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors) or (ii) has been 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 or mandating activities subject to, federal or
state securities laws, or finding any violation with respect to such laws.

Item 3.   Source and Amount of Funds or Other Consideration.
          -------------------------------------------------

          As more fully described in Item 4 below, pursuant to the terms of the
Stock Option Agreement (as defined below), BP Amoco will have the right, upon
the occurrence of certain events specified therein, to purchase up to 64,861,617
ARCO Common Shares (subject to possible adjustment as provided in the Stock
Option Agreement) at a price per share in cash equal to $82.82. If BP Amoco
purchases ARCO Common Shares pursuant to the Stock Option Agreement, BP Amoco
anticipates that the funds to finance such purchase would come from its working
capital and funds available for investment.


                                       -4-

<PAGE>


Item 4.   Purpose of the Transaction.
          --------------------------

          (a)-(j)  On March 31, 1999, ARCO, BP Amoco and Prairie Holdings, Inc.,
a Delaware corporation and wholly owned subsidiary of BP Amoco ("Merger Sub"),
entered into an Agreement and Plan of Merger, dated as of March 31, 1999 (the
"Merger Agreement"). The Merger Agreement provides, among other things, for the
merger of the Merger Sub with and into ARCO (the "Merger"), with ARCO being the
corporation surviving the Merger.

          Pursuant to the Merger Agreement, at the Effective Time (as defined in
the Merger Agreement), each ARCO Common Share issued and outstanding immediately
prior to the Effective Time (other than ARCO Common Shares that are owned by
ARCO, BP Amoco, or any subsidiary of BP Amoco or ARCO, other than CH-Twenty,
Inc., a Delaware corporation and subsidiary of ARCO ("C-H Twenty")
(collectively, "Excluded ARCO Shares")), will be converted into 4.92 ordinary
shares, of nominal value $0.50 each ("BP Amoco Ordinary Shares") of BP Amoco.
The BP Amoco Ordinary Shares to which holders of ARCO Common Shares are entitled
to be delivered in the form of American Depositary Shares, each representing
the right to receive six BP Amoco Ordinary Shares, subject to each such holder's
right to elect to receive BP Amoco Ordinary Shares in lieu of any or all of the
of BP Amoco Depositary Shares to which such holder is entitled. The Merger
Agreement also provides that each Excluded ARCO Share, except for shares owned
by C-H-Twenty, will be canceled and retired without payment of any consideration
therefor. At the Effective Time, ARCO will become a wholly owned subsidiary of
BP Amoco.

          Consummation of the Merger is subject to the satisfaction or waiver at
or prior to the Effective Time of certain conditions, including, but not limited
to, (i) approval of the Merger Agreement by the holders of ARCO Common Shares
and by the shareholders of BP Amoco and (ii) various regulatory conditions.

          Pursuant to the Merger Agreement, (i) the certificate of incorporation
of ARCO as in effect immediately prior to the Effective Time will be the
certificate of incorporation of ARCO as the corporation surviving the Merger,
unless the Merger Agreement is adopted by the holders of 66 2/3% of the
outstanding stock entitled to vote at the ARCO special meeting of stockholders,
in which case the certificate of incorporation of the corporation surviving the
merger shall be amended as set forth in Section 1.7.1 of the Merger Agreement,
(ii) the bylaws of Merger Sub in effect at the Effective Time shall be the
bylaws of the corporation surviving the Merger, and (iii) the directors of
Merger Sub at the Effective Time, and such officers as are mutually agreed by BP
Amoco and ARCO prior to the Effective Time will, from and after the Effective
Time, be the directors and officers, respectively, of ARCO as the corporation
surviving the Merger.


                                       -5-

<PAGE>


          The Merger Agreement contains certain customary restrictions on the
conduct of the businesses of ARCO and BP Amoco pending the Merger, including
certain customary restrictions relating to the capital stock of each. In
addition, ARCO has agreed in the Merger Agreement that after the date of the
Merger Agreement and prior to the Effective Time it will not declare, set aside
or pay any dividend payable in cash, stock or property in respect of any capital
stock, other than regular quarterly cash dividends not in excess of the
dividends paid by ARCO in the quarter ended December 31, 1998.

          The Merger Agreement is attached hereto as Exhibit 1 and is
incorporated herein by reference in its entirety. The foregoing summary of the
Merger Agreement does not purport to be complete and is qualified in its
entirety by reference to such exhibit.

          Concurrent with the execution of the Merger Agreement, BP Amoco and
ARCO also entered into a Stock Option Agreement, dated as of March 31, 1999 (the
"Stock Option Agreement"), a copy of which is attached hereto as Exhibit 2 and
is incorporated herein by reference. Pursuant to the Stock Option Agreement,
ARCO granted BP Amoco an unconditional, irrevocable option (the "Option") to
purchase, subject to the terms thereof, up to 64,861,617 (subject to possible
adjustment as provided therein) fully paid and nonassessable shares ("Option
Shares") of ARCO Common Shares, but in no event more than 19.9% of the ARCO
Common Shares issued and outstanding at the time of exercise (without giving
effect to the Option Shares issuable under the Option), at a price per share in
cash equal to $82.82 (the "Option Price"). The Option Price with respect to the
Option Shares as to which BP Amoco may propose to exercise the Option or to
request the repurchase of the Option shall be adjusted downward to the extent
necessary to be the Maximum Option Price (as defined below). The Stock Option
Agreement defines "Maximum Option Price" to be that price per share in cash at
which the Option must be exercisable in order to result in a Total Profit
(defined below) to BP Amoco, determined as of the date of such proposed
exercise, of $25 million, assuming that such option were exercised on such date
for all Option Shares subject to the Option and assuming that all of such Option
Shares were sold for cash at the closing market price on the New York Stock
Exchange, Inc. (the "NYSE") for the ARCO Common Shares as of the close of
business on the preceding trading day (less customary brokerage commissions).

          In the event that any additional ARCO Common Shares are issued or
otherwise become outstanding after the date of the Stock Option Agreement (other
than pursuant to the Stock Option Agreement), the aggregate number of Option
Shares purchasable upon exercise of the Option shall automatically be increased
(without any further action on the part of ARCO or BP Amoco being necessary) so
that, taking into consideration any such issuance, such aggregate number equals
19.9% of the ARCO Common Shares issued and outstanding.

          The Stock Option Agreement provides that BP Amoco must exercise the
Option in whole but not in part (except as otherwise permitted under the Stock
Option


                                       -6-

<PAGE>


Agreement), by delivering a written notice thereof (in accordance with the terms
of the Stock Option Agreement) within 180 days following the occurrence of a
Triggering Event (as defined below), unless prior to such Triggering Event the
Effective Time has occurred.The Option will terminate upon either (i) the 
occurrence of the Effective Time or (ii) the close of business on the earlier of
(x) the date 180 days after the date on which a Triggering Event occurs and 
(y) the date on which it is no longer possible for a Triggering Event to occur,
provided that no Triggering Event shall have occurred prior to or upon such 
date.

          For purposes of the Stock Option Agreement, a "Triggering Event" will
be deemed to have occurred if the Merger Agreement is terminated and BP Amoco
then or thereafter becomes entitled to receive an aggregate of $450 million
(taking into account any amounts to which BP Amoco will have theretofore become
entitled) as the ARCO Termination Amount pursuant to Section 5.5.2 of the Merger
Agreement.

          Pursuant to the Stock Option Agreement, if BP Amoco is entitled to and
wishes to exercise the Option, it has agreed to send ARCO a written notice (the
date of which is referred to as the "Notice Date") specifying (i) the total
amount payable to ARCO on the exercise of the Option and (ii) a place and date
(a "Closing Date") not earlier than three business days nor later than 60
business days from the Notice Date for the closing of such purchase (a
"Closing"). However, the notice period may be delayed, as specified in the Stock
Option Agreement, for any filing that may be required under the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, or any prior
notification to or approval of any other regulatory authority in the U.S., U.K.
or elsewhere that may be required in connection with such purchase.

          The Stock Option Agreement further provides that upon occurrence of a
Triggering Event, at the request of BP Amoco, subject to provisions in the
certificate of incorporation of ARCO setting forth any restrictions on such
repurchase, ARCO will repurchase, (i) the Option in whole but not in part
(except as otherwise permitted under the Stock Option Agreement), at a price
equal to the number of Option Shares then purchasable upon exercise of the
Option multiplied by the amount by which the Market Price (as defined in the
Stock Option Agreement) exceeds the applicable Option Price (giving effect to
the Maximum Option Price), or (ii) all Option Shares then owned by BP Amoco at a
price equal to the number of such shares multiplied by the Market Price.

          In addition, the Stock Option Agreement provides that, notwithstanding
any other provision of the Stock Option Agreement, in no event will BP Amoco's
Total Profit (as defined below) plus any ARCO Termination Amount exceed in the
aggregate $500 million and, if it otherwise would exceed such amount, BP Amoco,
at its sole election, is required to either (a) reduce the number of Option
Shares subject to the Option, (b) deliver to ARCO for cancellation Option Shares
previously purchased by BP Amoco, (c) pay cash to ARCO, or (d) any combination
thereof, so that BP Amoco's actually realized Total Profit when aggregated with
the ARCO Termination Amount (or


                                       -7-

<PAGE>


part thereof) so paid to BP Amoco does not exceed $500 million after taking
into account the foregoing actions. The Stock Option Agreement defines "Total
Profit" to mean the aggregate amount (before tax) of the following: (i) (x) the
amount received by BP Amoco pursuant to ARCO's repurchase of the Option or any
Option Shares, less, in the case of any repurchase of Option Shares, (y) BP 
Amoco's purchase price for such Option Shares, as the case may be, (ii) (x)
the fair market value, or the aggregate net cash amounts received by BP Amoco
pursuant to the sale, of Option Shares (or (A) any other securities into which
such Option Shares are converted or exchanged or (B) any property, cash or other
securities received pursuant to adjustments made under Section 7 of the Stock
Option Agreement), less (y) BP Amoco's purchase price of such Option Shares.

          The Stock Option Agreement also provides that notwithstanding any
other provision of the Stock Option Agreement to the contrary, the Option may
not be exercised for a number of shares as would, as of the date of exercise,
result in a Notional Total Profit (as described below) which, together with any
ARCO Termination Amount heretofore paid to BP Amoco, would exceed $500 million.
As used in the Stock Option Agreement, the term "Notional Total Profit" with
respect to the Option Shares will be the Total Profit determined as of the date
of such proposal assuming that the Option was exercised in full on such date and
assuming that (i) such Option Shares were sold for cash at the closing market
price on the NYSE for ARCO Common Shares as of the close of business on the
preceding trading day (less customary brokerage commissions) and (ii) any
Additional Property was sold at fair market value.

          The foregoing summary of the Stock Option Agreement does not purport
to be complete and is qualified in its entirety by reference to the text of the
Stock Option Agreement attached as Exhibit 2 hereto.

          Except as set forth in this Statement, the Merger Agreement or the
Stock Option Agreement, neither BP Amoco or, to the best of BP Amoco's
knowledge, any of the individuals named in Schedule I hereto, has any plans or
proposals which relate to or which would result in or relate to any of the
actions specified in sub-paragraphs (a) through (j) of Item 4 of Schedule 13D.

Item 5.   Interest in Securities of the Issuer.
          ------------------------------------

          (a) - (b)  By reason of its execution of the Stock Option Agreement,
BP Amoco might be deemed to have beneficial ownership of and sole voting and
dispositive power with respect to the ARCO Common Shares subject to the Option
and, accordingly, might be deemed to beneficially own 64,861,617 ARCO Common
Shares as a result of the Stock Option Agreement. Based on the number of ARCO
Common Shares subject to the Option as of March 31, 1999, BP Amoco would
beneficially own approximately 19.9% of the outstanding ARCO Common Shares
(based upon the 325,937,777 ARCO Common Shares outstanding on March 26, 1999, as
represented to BP Amoco by ARCO in the Merger Agreement) following exercise of
the Option for



                                       -8-

<PAGE>


64,861,617 ARCO Common Shares. However, BP Amoco expressly disclaims any
beneficial ownership of the 64,861,617 ARCO Common Shares which are obtainable
by BP Amoco upon exercise of the Option, because the Option is exercisable only
in the circumstances set forth in Item 4 above, none of which has occurred as of
the date hereof.

         Neither BP Amoco nor, to the best of BP Amoco's knowledge, any of the
individuals named in Schedule I hereto, unless otherwise indicated therein, owns
any ARCO Common Shares.

          (c)  Neither BP Amoco nor, to the best of BP Amoco's knowledge, any of
the individuals named in Schedule I hereto, has effected any transaction in ARCO
Common Shares during the past 60 days.

          (d)  Prior  to the  Effective  Time  and so long as BP  Amoco  has not
purchased ARCO Common Shares  subject to the Option,  BP Amoco does not have the
right to receive or the power to direct the receipt of  dividends  from,  or the
proceeds from the sale of, any ARCO Common Shares.

          (e)  Not applicable.

Item 6.   Contracts, Arrangements, Understandings or Relationships with Respect
          to Securities of the Issuer.
          ---------------------------------------------------------------------

          Except as provided in the Merger Agreement, the Stock Option Agreement
or as set forth in this Statement, neither BP Amoco nor, to the best of BP
Amoco's knowledge, any of the individuals named in Schedule I hereto, has any
contracts, arrangements, understandings or relationships (legal or otherwise)
with any person with respect to any securities of ARCO, including, but not
limited to, transfer or voting of any of the securities, finder's fees, joint
ventures, loan or option arrangements, puts or calls, guarantees of profits,
division of profits or losses, or the giving or withholding of proxies.

Item 7.   Material to be filed as Exhibits.
          --------------------------------

          Exhibit           1 -- Agreement and Plan of Merger, dated as
                                 of March 31, 1999, among Atlantic Richfield
                                 Company, BP Amoco p.l.c.
                                 and Prairie Holdings, Inc.

          Exhibit           2 -- Stock Option Agreement, dated as of
                                 March 31, 1999 between Atlantic Richfield
                                 Company and BP Amoco p.l.c.



                                       -9-

<PAGE>


                                    SIGNATURE

          After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this Statement is true, complete and
correct.

Dated:  April 9, 1999
                                        BP AMOCO p.l.c.



                                        By:    /s/ Gillian Young        
                                               -----------------------------
                                        Name:  G. E. Young
                                        Title: Deputy Assistant Secretary



                                      -10-


<PAGE>



                                   SCHEDULE I
                                   ----------

                       DIRECTORS AND EXECUTIVE OFFICERS OF
                                 BP AMOCO P.L.C.

          The name, citizenship, present principal occupation or employment, and
the name of any corporation or other organization in which such employment is
conducted, of each of the directors and executive officers of BP Amoco p.l.c.
("BP Amoco") is set forth below. Except as set forth below, each of the
directors and executive officers is a citizen of the United Kingdom. The
business address of each director and officer is BP Amoco p.l.c., Britannic
House, 1 Finsbury Circus, London EC2M 7BA, England. Unless otherwise indicated,
each occupation set forth opposite an executive officer's name refers to
employment with BP Amoco.

Name and Business                 Present Principal Occupation or Employment
- - -----------------                 ------------------------------------------
                                  (Executive Officer positions noted, where
Directors                          applicable)

P.D. Sutherland                   Non-executive Co-Chairman, Chairman of
(Ireland)                         Goldman Sachs International

H. L. Fuller                      Executive Co-Chairman
(United States)

Sir Ian Prosser                   Non-executive Deputy Chairman, Chairman and
                                  Chief Executive of Bass PLC

Sir John Browne                   Executive Director and Group Chief Executive

Dr. J. G. S. Buchanan             Executive Director and Chief Financial Officer
(British and New Zealand)

R. F. Chase                       Executive Director and Deputy Group Chief
                                  Executive

Dr. C. S. Gibson-Smith            Executive Director, Regions and Policies

R. L. Olver                       Executive Director, Exploration and Production

B. K. Sanderson                   Executive Director, Chemicals

R. S. Block                       Non-executive Director, retired Executive Vice
(United States)                   President and Chief Insurance Officer, The 
                                  Equitable


                                       -1-

<PAGE>


J. H. Bryan                       Non-executive Director, Chairman and Chief
(United States)                   Executive Officer of Sara Lee Corporation

E. B. Davis, Jr.                  Non-executive Director, President and Chief
(United States)                   Executive Officer of Alliant Energy

R. J. Ferris                      Non-executive Director, retired Co-chairman of
(United States)                   Doubletree Corporation

C. F. Knight                      Non-executive Director, Chairman and Chief
(United States)                   Executive Officer of Emerson Electric

F. A. Maljers                     Non-executive Director, Chairman of the
(Netherlands)                     Supervisory Board of the Amsterdam
                                  Concertgebouw N.V.

Dr. W. E. Massey                  Non-executive Director, President of Morehouse
(United States)                   College
H. M. P. Miles                    Non-executive Director, Chairman of Johnson
                                  Matthey

Sir Robin Nicholson               Non-executive Director, retired Chairman of
                                  Pilkington Optronics

M. H. Wilson                      Non-executive Director, Vice Chairman and
(Canada)                          Director of RBC Dominion Securities, Inc.

R. P. Wilson                      Non-executive Director, Chairman of Rio Tinto
                                  plc

The Lord Wright of Richmond       Non-executive Director, Chairman of the Royal
                                  Institute of International Affairs

Executive Officers
- - ------------------

J. C. Hanratty                    Company Secretary
(New Zealand)


                                       -2-

<PAGE>
                          EXHIBIT INDEX

Exhibit Number                 Description

      1                    Agreement and Plan of Merger, dated as
                           of March 31, 1999, among Atlantic Richfield
                           Company, BP Amoco p.l.c.
                           and Prairie Holdings, Inc.

      2                    Stock Option Agreement, dated as of
                           March 31, 1999 between Atlantic Richfield
                           Company and BP Amoco p.l.c.




                                                                       EXHIBIT 1











                               AGREEMENT AND PLAN

                                    OF MERGER

                                      Among

                                BP AMOCO p.l.c.,

                           ATLANTIC RICHFIELD COMPANY

                                       and

                             PRAIRIE HOLDINGS, INC.

                           Dated as of March 31 , 1999










<PAGE>
                                TABLE OF CONTENTS


                                                                    Page


                                    ARTICLE I

                           THE CLOSING AND THE MERGER

1.1.  Closing........................................................2
1.2.  The Merger.....................................................2
1.3.  Conversion and Exchange of Shares..............................3
1.4.  Surrender and Payment..........................................5
1.5.  ARCO Stock Options; Other Stock-Based Plans....................7
1.6.  Fractional BP Amoco Shares....................................10
1.7.  The Surviving Corporation.....................................11
1.8.  Lost, Stolen or Destroyed Certificates........................11


                                   ARTICLE II

                         REPRESENTATIONS AND WARRANTIES

2.1.  Representations and Warranties of BP Amoco and ARCO...........11
      2.1.1.   Organization, Good Standing and Qualification........12
      2.1.2.   Capital Structure....................................13
      2.1.3.   Corporate Authority; Approval and Fairness...........15
      2.1.4.   Governmental Filings; No Violations..................17
      2.1.5.   Reports; Financial Statements........................18
      2.1.6.   Absence of Certain Changes...........................20
      2.1.7.   Litigation and Liabilities...........................21
      2.1.8.   Takeover Statutes....................................22
      2.1.9.   Brokers and Finders..................................22
      2.1.10.  Ownership of Other Party's Common Stock..............22
      2.1.11.  Merger Sub...........................................23
      2.1.12.  ARCO Employee Benefit Plans..........................23
      2.1.13.  Environmental Matters................................24
      2.1.14.  ARCO Rights Plan.....................................24
      2.1.15.  ARCO Joint Ventures; Exclusivity Arrangements........25
      2.1.16.  Tax Matters..........................................25
2.2.  Vastar........................................................25




<PAGE>



                                   ARTICLE III

                                    COVENANTS

3.1.  Interim Operations............................................26
      3.1.1.   Interim Operations of BP Amoco.......................26
      3.1.2.   Interim Operations of ARCO...........................27
      3.1.3.   Consultation as to Material Contracts................32
3.2.  ARCO Acquisition Proposals....................................33
3.3.  Information Supplied..........................................34
      3.3.1.   Registration Statement...............................34
      3.3.2.   BP Amoco Documents...................................36
3.4.  Shareholders Meetings.........................................37
3.5.  Filings; Other Actions; Notification..........................38
3.6.  Access........................................................40
3.7.  Publicity.....................................................40
3.8.  Benefits and Other Matters....................................41
      3.8.1.   Employee Benefits....................................41
      3.8.2.   Director and Officer Liability.......................43
3.9.  Expenses......................................................44
3.10. Takeover Statutes.............................................44
3.11. Dividends.....................................................44
3.12. Listing Applications..........................................45
3.13. Letters of Accountants........................................45
3.14. Agreements of ARCO Affiliates.................................45
3.15. Accounting Matters............................................46
3.16. Tax Matters...................................................46
3.17. Vastar........................................................46
3.18. Section 103...................................................46


                                   ARTICLE IV

                                   CONDITIONS

4.1.  Conditions to Each Party's Obligation to Effect the Merger....46
      4.1.1.   Shareholder Approvals................................47
      4.1.2.   Regulatory Consents..................................47
      4.1.3.   Laws and Orders......................................47
      4.1.4.   Effectiveness of Form F-4............................47
      4.1.5.   Exchange Listings....................................48
4.2.  Conditions to Obligations of BP Amoco and Merger Sub..........48
      4.2.1.   Representations and Warranties of ARCO...............48
      4.2.2.   Performance of Obligations of ARCO...................48


<PAGE>



4.3.  Conditions to Obligation of ARCO..............................48
      4.3.1.   Representations and Warranties.......................48
      4.3.2.   Performance of Obligations of BP Amoco...............49
      4.3.3.   Tax Opinion..........................................49


                                    ARTICLE V

                                   TERMINATION

5.1.  Termination by Mutual Consent.................................49
5.2.  Termination by Either BP Amoco or ARCO........................49
5.3.  Termination by BP Amoco.......................................50
5.4.  Termination by ARCO...........................................50
5.5.  Effect of Termination and Abandonment.........................51


                                   ARTICLE VI

                            MISCELLANEOUS AND GENERAL

6.1.  Survival......................................................53
6.2.  Modification or Amendment.....................................53
6.3.  Waiver........................................................53
6.4.  Failure or Indulgence Not Waiver; Remedies Cumulative.........53
6.5.  Counterparts..................................................53
6.6.  GOVERNING LAW AND VENUE; WAIVER OF JURY TRIAL.................54
6.7.  Notices.......................................................55
6.8.  Entire Agreement..............................................56
6.9.  Obligations of BP Amoco and of ARCO...........................57
6.10. Severability..................................................57
6.11. Interpretation................................................57
6.12. Assignment....................................................58



<PAGE>



                             Index of Defined Terms


Affiliate...........................................................13
Agreement............................................................1
ARCO.................................................................1
ARCO $2.80 Preference Stock.........................................14
ARCO $3.00 Preference Stock.........................................14
ARCO Acquisition Proposal...........................................33
ARCO Affiliates.....................................................46
ARCO Alternative Agreement..........................................52
ARCO Audit Date.....................................................20
ARCO Common Shares...................................................1
ARCO Compensation and Benefit Plans.................................23
ARCO Disclosure Letter..............................................12
ARCO Executive Officers.............................................21
ARCO Preference Stock...............................................14
ARCO Preferred Stock................................................14
ARCO Proxy Statement................................................35
ARCO Reports........................................................20
ARCO Representatives................................................33
ARCO Required Consents..............................................17
ARCO Requisite Vote.................................................16
ARCO Stock Option....................................................7
ARCO Stock Plans....................................................14
ARCO Stockholders Meeting...........................................37
ARCO Termination Amount.............................................52
Audit Date..........................................................20
Bankruptcy and Equity Exception.....................................16
BP Amoco.............................................................1
BP Amoco 20-F.......................................................19
BP Amoco ADRs........................................................3
BP Amoco Audit Date.................................................19
BP Amoco Circular...................................................36
BP Amoco Depositary Shares...........................................3
BP Amoco Disclosure Letter..........................................12
BP Amoco Documents..................................................36
BP Amoco Executive Directors........................................21
BP Amoco First Preference Shares....................................13
BP Amoco Listing Document...........................................36
BP Amoco Ordinary Share..............................................3
BP Amoco Reports....................................................19
BP Amoco Required Consents..........................................17
BP Amoco Requisite Vote.............................................15
BP Amoco Second Preference Shares...................................13


<PAGE>



BP Amoco Shareholder Meeting........................................37
BP Amoco Shares......................................................5
BP Amoco Termination Amount.........................................53
BP Amoco Voting Shares..............................................15
Canceled ARCO Share..................................................3
Certificate..........................................................3
Certificate of Merger................................................2
CH-Twenty............................................................3
CH-Twenty ARCO Shares................................................3
Closing..............................................................2
Closing Date.........................................................2
Code.................................................................1
Companies Act.......................................................12
Confidentiality Agreement...........................................40
Constituent Corporations.............................................1
Contracts...........................................................18
Deposit Agreement....................................................3
Depositary...........................................................3
DGCL.................................................................1
Directors' Plan.....................................................10
Disclosure Letter...................................................12
Effective Time.......................................................3
Eligible ARCO Shareholders...........................................1
ELTIP................................................................8
Encumbrance.........................................................13
Environmental Law...................................................24
ERISA...............................................................23
Exchange Act........................................................13
Exchange Agent.......................................................5
Exchange Ratio.......................................................3
Excluded ARCO Shares.................................................3
Exclusivity Agreements..............................................25
Exon-Florio.........................................................17
Form F-4............................................................35
FSA.................................................................36
Governmental Consents...............................................47
Governmental Entity.................................................17
Hazardous Substance.................................................24
HSR Act.............................................................17
Indemnitees.........................................................43
IPA.................................................................43
Joint Venture Agreements............................................25
Law.................................................................18
LSE.................................................................10
Material Adverse Effect.............................................12


<PAGE>


Merger...............................................................1
Merger Consideration.................................................3
Merger Sub...........................................................1
Merger Sub Common Stock..............................................4
MMC.................................................................17
NYSE................................................................10
Option Schemes......................................................13
Order...............................................................47
Parties..............................................................1
Party................................................................1
Person..............................................................13
Regulation..........................................................17
Reports.............................................................20
Rights..............................................................24
Rights Agreement....................................................24
SEC.................................................................10
Securities Act......................................................10
Share Election.......................................................5
Stock Option Agreement...............................................1
Subsidiary..........................................................12
Superior Proposal...................................................33
Surviving Corporation................................................2
Takeover Panel......................................................17
Takeover Statute....................................................22
Termination Date....................................................50
U.K. GAAP...........................................................19
U.S. GAAP...........................................................20
Vastar..............................................................15



<PAGE>




         This AGREEMENT AND PLAN OF MERGER, dated as of March 31, 1999 (this
"Agreement"), among BP AMOCO p.l.c. ("BP Amoco"), an English public limited
company, ATLANTIC RICHFIELD COMPANY, a Delaware corporation ("ARCO"), and
PRAIRIE HOLDINGS, INC., a Delaware corporation and a direct wholly owned
subsidiary of BP Amoco ("Merger Sub" and, together with ARCO, the "Constituent
Corporations");

                              W I T N E S S E T H :

         WHEREAS, the respective Boards of Directors of each of ARCO, BP Amoco
and Merger Sub (each, a "Party" and, together, the "Parties") have each
determined that it is in the best interests of their respective companies and
stockholders or shareholders, as the case may be, to combine their respective
businesses;

         WHEREAS, in furtherance of such combination, the respective Boards of
Directors of ARCO and Merger Sub have each adopted resolutions approving this
Agreement and declaring its advisability and approving the merger (the "Merger")
of Merger Sub with and into ARCO in accordance with the Delaware General
Corporation Law, as amended (the "DGCL"), upon the terms and subject to the
conditions set forth herein;

         WHEREAS, in furtherance of such combination, the Board of Directors of
BP Amoco adopted a resolution approving this Agreement and the Merger, upon the
terms and subject to the conditions set forth herein;

         WHEREAS, it is intended that, for U.S. federal income tax purposes, the
Merger shall qualify as a reorganization under the provisions of Section 368(a)
of the Internal Revenue Code of 1986, as amended, and the rules and regulations
promulgated thereunder (the "Code") and that the holders of ARCO Common Shares
who will not be "five percent transferee shareholders" as defined in Treasury
Regulation Section 1.367(a)- 3(c)(5)(ii) or who enter into five-year gain
recognition agreements in the form provided in Treasury Regulation Section
1.367(a)-8(b) ("Eligible ARCO Shareholders") not recognize taxable gain with
respect to the Merger pursuant to Section 367(a) of the Code (except with
respect to cash received in lieu of fractional share interests);

         WHEREAS, as an inducement to the willingness of BP Amoco to enter into
this Agreement, the Board of Directors of ARCO has approved the grant to BP
Amoco of an option to purchase shares of common stock, par value $2.50 per
share, of ARCO ("ARCO Common Shares") pursuant to a stock option agreement,
dated as of March 31, 1999, between ARCO and BP Amoco (the "Stock Option
Agreement"), and each of ARCO and BP Amoco has duly authorized, executed and
delivered the Stock Option Agreement; and


<PAGE>



         WHEREAS, ARCO and BP Amoco desire to make certain representations,
warranties, covenants and agreements in connection with this Agreement.

         NOW, THEREFORE, in consideration of the mutual representations,
warranties, covenants and agreements contained herein, the parties hereto,
intending to be legally bound, hereby agree as follows:

                                    ARTICLE I

                           The Closing and the Merger

         1.1. Closing. The closing of the Merger (the "Closing") shall take
place (i) at the offices of Linklaters & Paines, One Silk Street, London,
England, with a meeting to be held simultaneously at the offices of Sullivan &
Cromwell, 125 Broad Street, New York, New York, for the delivery of certain
documents in connection therewith, at a time to be agreed by the Parties on the
third business day after the day on which the last to be fulfilled or waived of
the conditions set forth in Article IV (other than those conditions that by
their nature are to be fulfilled at the Closing, but subject to the fulfillment
or waiver of such conditions) shall be fulfilled or waived in accordance with
this Agreement or (ii) at such other places and time and/or on such other date
as ARCO and BP Amoco may agree in writing (the "Closing Date").

         1.2. The Merger.

         1.2.1. Upon the terms and subject to the conditions set forth in this
     Agreement, at the Effective Time (as defined in Section 1.2.2), Merger Sub
     shall be merged with and into ARCO in accordance with the DGCL, whereupon
     the separate existence of Merger Sub shall cease, and ARCO shall be the
     surviving corporation in the Merger (the "Surviving Corporation") and shall
     continue to be governed by the laws of the State of Delaware, and the
     separate corporate existence of ARCO, with all its rights, privileges,
     immunities, powers and franchises, shall continue unaffected by the Merger
     except as set forth in this Article I. The Merger shall have the effects
     specified in the DGCL.

         1.2.2. As soon as practicable after satisfaction or waiver (to the
     extent herein permitted) of the conditions to the obligations of the
     Parties to consummate the Merger set forth in Article IV, ARCO and Merger
     Sub will cause a certificate of merger (the "Certificate of Merger") to be
     executed and filed with the Secretary of State of the State of Delaware and
     make all other filings or recordings required by applicable law in
     connection with the Merger. The Merger shall become effective at such time
     as the Certificate of Merger is duly filed with the Secretary 



                                -2-
<PAGE>


     of State of the State of Delaware or at such later time as is specified in
     the Certificate of Merger in accordance with the DGCL (the "Effective
     Time").
 
         1.3. Conversion and Exchange of Shares. At the Effective Time:

         1.3.1. Each ARCO Common Share owned by BP Amoco, ARCO or any Subsidiary
     (as defined in Section 2.1.1) of BP Amoco or ARCO (other than CH-Twenty,
     Inc. , a Delaware corporation and a Subsidiary of ARCO ("CH-Twenty"))
     immediately prior to the Effective Time (each, a "Canceled ARCO Share")
     shall, by virtue of the Merger, and without any action on the part of the
     holder thereof, no longer be outstanding, shall be canceled and retired
     without payment of any consideration therefor and shall cease to exist. The
     ARCO Common Shares owned by CH-Twenty immediately prior to the Merger (if
     any) (the "CH-Twenty ARCO Shares" and, together with the Canceled ARCO
     Shares, the "Excluded ARCO Shares") shall remain outstanding, without
     change, after the Effective Time, and no consideration shall be delivered
     in exchange therefor.

         1.3.2. Each ARCO Common Share outstanding immediately prior to the
     Effective Time, other than Excluded ARCO Shares, shall be converted into
     and shall be canceled in exchange for the right to receive 4.92 (the
     "Exchange Ratio") ordinary shares, of nominal value $0.50 each, of BP Amoco
     (each, a "BP Amoco Ordinary Share"), which shall be delivered to the
     holders of ARCO Common Shares (other than Excluded ARCO Shares) (i) in the
     form of American depositary shares (the "BP Amoco Depositary Shares"), each
     representing the right to receive six BP Amoco Ordinary Shares, or (ii) if
     and to the extent elected by any such holder in the manner provided in
     Section 1.4.1, in the form of BP Amoco Ordinary Shares, in registered form,
     rather than BP Amoco Depositary Shares (the "Merger Consideration"). The BP
     Amoco Depositary Shares may be evidenced by one or more receipts ("BP Amoco
     ADRs") issued in accordance with the Amended and Restated Deposit
     Agreement, dated as of December 31, 1998, among BP Amoco, Morgan Guaranty
     Trust Company of New York, as Depositary (the "Depositary"), and the
     holders from time to time of BP Amoco ADRs (the "Deposit Agreement"). At
     the Effective Time, all ARCO Common Shares (other than any CH-Twenty ARCO
     Shares) shall no longer be outstanding, shall be canceled and retired and
     shall cease to exist, and each certificate (a "Certificate") formerly
     representing any of such ARCO Common Shares (other than Excluded ARCO
     Shares) shall thereafter represent only the right to the Merger
     Consideration and the right, if any, to receive pursuant to Section 1.6
     cash in lieu of fractional BP Amoco Depositary Shares (or, if applicable,
     fractional BP Amoco Ordinary Shares) and any dividend or distribution
     pursuant to Section 1.4.6, in each case without interest. BP Amoco shall,
     following the Closing, pay all stamp duties, stamp duty reserve tax and
     other taxes and similar levies imposed in connection with the


                                       -3-

<PAGE>



     issuance or creation of the BP Amoco Ordinary Shares, BP Amoco Depositary
     Shares and any BP Amoco ADRs in connection therewith.

         1.3.3.  Each share of common stock of Merger Sub, par value $.001 per
     share ("Merger Sub Common Stock"), outstanding immediately prior to the
     Effective Time shall be canceled and, in consideration for the issuance of
     the BP Amoco Ordinary Shares referred to in Section 1.3.4, the Surviving
     Corporation shall issue to BP Amoco at the Effective Time such number of
     shares of common stock as is equal to the number of ARCO Common Shares
     outstanding immediately prior to the Effective Time (excluding any
     CH-Twenty ARCO Shares) with the same rights, powers and privileges as the
     ARCO Common Shares, which shares of common stock, together with the
     CH-Twenty ARCO Shares, shall constitute the only outstanding shares of
     common stock of the Surviving Corporation.

         1.3.4.  In consideration of the issue to BP Amoco by the Surviving
     Corporation of shares of common stock of the Surviving Corporation pursuant
     to Section 1.3.3, BP Amoco shall issue, in accordance with Section 1.4,
     such number of BP Amoco Ordinary Shares as is equal to the number of ARCO
     Common Shares outstanding immediately prior to the Effective Time (other
     than the Excluded ARCO Shares) multiplied by the Exchange Ratio to permit
     (i) the issuance of BP Amoco Depositary Shares and (ii) if elected by any
     holder of ARCO Common Shares in the manner provided in Section 1.4.1, the
     delivery of BP Amoco Ordinary Shares, in registered form, to the holders of
     such ARCO Common Shares for the purpose of giving effect to the delivery of
     the Merger Consideration referred to in Section 1.3.2.

         1.3.5. In the event that, subsequent to the date of this Agreement but
     prior to the Effective Time, ARCO changes the number of ARCO Common Shares,
     or BP Amoco changes the number of BP Amoco Ordinary Shares, issued and
     outstanding as a result of a stock split, stock combination, stock
     dividend, recapitalization, redenomination of share capital or other
     similar transaction, the Exchange Ratio and other items dependent thereon
     shall be appropriately adjusted.

         1.3.6. Each share of ARCO $3.00 Preference Stock and each share of ARCO
     $2.80 Preference Stock (each as defined in Section 2.1.2.2) outstanding
     immediately prior to the Effective Time shall remain outstanding, without
     change, after the Effective Time, and no consideration shall be delivered
     in exchange therefor; provided, however, BP Amoco agrees that from and
     after the Effective Time, the number of BP Amoco Ordinary Shares into which
     each share of ARCO $3.00 Preference Stock and each share of ARCO $2.80
     Preference Stock shall be convertible shall be equal in each case to the
     number of ARCO Common Shares


                                 -4-

<PAGE>



     into which such share was convertible immediately prior to the Effective
     Time, multiplied by the Exchange Ratio (without any adjustment pursuant to
     Section 1.3.5 in the conversion rates between such ARCO Preference Stock
     and ARCO Common Shares for changes in ARCO Common Shares prior to the
     Effective Time, for which changes the terms of the ARCO $3.00 Preference
     Stock and the ARCO $2.80 Preference Stock contained in the restated
     certificate of incorporation of ARCO shall provide the relevant adjustment,
     if any).

         1.4.  Surrender and Payment.

         1.4.1. Prior to the Effective Time, BP Amoco shall appoint an agent
     reasonably acceptable to ARCO as exchange agent (the "Exchange Agent") for
     the purpose of exchanging Certificates for BP Amoco Depositary Shares or,
     if and to the extent elected by a holder of a Certificate in the manner
     provided in this Section 1.4.1, for BP Amoco Ordinary Shares in registered
     form. Promptly after the Effective Time, the Surviving Corporation will
     send, or will cause the Exchange Agent to send, to each holder of record as
     of the Effective Time of ARCO Common Shares (other than holders of Excluded
     ARCO Shares) (i) a letter of transmittal, in such form as ARCO and BP Amoco
     may reasonably agree, for use in effecting delivery of ARCO Common Shares
     to the Exchange Agent, which letter of transmittal shall include a form of
     election by which each such holder may elect to receive (the "Share
     Election") all or any part of the Merger Consideration to which such holder
     is entitled in the form of BP Amoco Ordinary Shares in registered form,
     rather than in the form of BP Amoco Depositary Shares (such BP Amoco
     Ordinary Shares or BP Amoco Depositary Shares to be received by a holder
     being referred to in this Agreement as "BP Amoco Shares") and (ii)
     instructions for surrendering Certificates in exchange for the BP Amoco
     Shares, and any cash in lieu of fractional shares and any cash dividends or
     other distributions, that such holder has the right to receive pursuant to
     this Article I.

         1.4.2. Each holder of any ARCO Common Shares that have been converted
     into a right to receive the consideration set forth in Section 1.3.2 shall,
     upon surrender to the Exchange Agent of a Certificate or Certificates,
     together with a properly completed letter of transmittal covering the ARCO
     Common Shares represented by such Certificate or Certificates, be entitled
     to receive (i) the number of whole BP Amoco Shares to which such holder is
     entitled in respect of such ARCO Common Shares pursuant to Section 1.3.2
     (after giving effect to any Share Election made by such holder) and (ii) a
     check in the amount (after giving effect to any required tax withholdings)
     of (A) any cash in lieu of fractional shares to be paid pursuant to Section
     1.6, plus (B) any cash dividends or other distributions that such holder
     has the right to receive pursuant to Section 1.4.6. Until so surrendered,
     each Certificate shall, after the Effective Time, represent for 


                                       -5-

<PAGE>



     all purposes only the right to receive the number of whole BP Amoco Shares
     to which such holder is entitled and the applicable amounts provided in the
     foregoing clause (ii).

         1.4.3. If any BP Amoco Shares are to be issued to a person other than
     the registered holder of the ARCO Common Shares represented by a
     Certificate or Certificates surrendered with respect thereto, it shall be a
     condition to such issue that the Certificate or Certificates so surrendered
     shall be properly endorsed or otherwise be in proper form for transfer and
     that the person requesting such issue shall pay to the Exchange Agent any
     transfer or other taxes required as a result of such issue to a person
     other than the registered holder of such ARCO Common Shares or establish to
     the satisfaction of the Exchange Agent that such tax has been paid or is
     not payable.

         1.4.4. After the close of the stock transfer books of ARCO on the day
     prior to the Effective Time, there shall be no further registration of
     transfers of ARCO Common Shares that were outstanding prior to the
     Effective Time. After the Effective Time, Certificates presented to the
     Surviving Corporation for transfer shall be canceled and exchanged for the
     consideration provided for, and in accordance with the procedures set
     forth, in this Article I.

         1.4.5.  Any BP Amoco Shares issued and delivered in respect of ARCO
     Common Shares pursuant to this Article I and any cash in lieu of fractional
     interests in BP Amoco Shares to be paid pursuant to Section 1.6, plus any
     cash dividend or other distribution that such holder has the right to
     receive pursuant to Section 1.4.6, that remains unclaimed by any holder of
     ARCO Common Shares six months after the Effective Time shall be held by the
     Exchange Agent (or a successor agent appointed by BP Amoco) or shall be
     delivered to the Depositary upon the instruction of BP Amoco and held by
     the Depositary, in either case subject to the instruction of BP Amoco in an
     account or accounts designated for such purpose. BP Amoco shall not be
     liable to any holder of ARCO Common Shares for any securities delivered or
     any amount paid by the Depositary or the Exchange Agent, as the case may
     be, to a public official pursuant to applicable abandoned property laws.
     Any cash remaining unclaimed by holders of ARCO Common Shares three years
     after the Effective Time (or such earlier date immediately prior to such
     time as such cash would otherwise escheat to or become property of any
     governmental entity or as is otherwise provided by applicable Law (as
     defined in Section 2.1.4.2)) shall, to the extent permitted by applicable
     Law, become the property of the Surviving Corporation or BP Amoco, as BP
     Amoco may determine.


                                       -6-

<PAGE>



         1.4.6.  No dividends, interest or other distributions with respect to
     securities of BP Amoco or the Surviving Corporation issuable with respect
     to ARCO Common Shares shall be paid to the holder of any unsurrendered
     Certificates until such Certificates are surrendered as provided in this
     Section. Subject to the effect of applicable Law, upon such surrender,
     there shall be issued and/or paid to the holder of the BP Amoco Shares
     issued in exchange therefor, without interest, (A) at the time of such
     surrender, the dividends or other distributions payable with respect to
     such BP Amoco Shares with a record date after the Effective Time and a
     payment date on or prior to the date of such surrender and not previously
     paid and (B) at the appropriate payment date, the dividends or other
     distributions payable with respect to such BP Amoco Shares with a record
     date after the Effective Time but with a payment date subsequent to such
     surrender. For purposes of dividends or other distributions in respect of
     BP Amoco Shares, all BP Amoco Shares to be issued pursuant to the Merger
     shall be deemed issued and outstanding as of the Effective Time.

         1.4.7.  The Parties may, by mutual agreement and without amending this
     Agreement in accordance with Section 6.2, make any modifications to the
     terms of or procedures for the Share Election, provided that any such
     modification will not adversely affect the entitlement of holders of ARCO
     Common Shares to the Merger Consideration and that such modification shall
     be filed with the Secretary of ARCO and made available to the stockholders
     of ARCO, without cost, upon request.

         1.5. ARCO Stock Options; Other Stock-Based Plans.

         1.5.1. At the Effective Time, each stock option to purchase ARCO Common
     Shares under any ARCO Stock Plan (as defined in Section 2.1.2.2) (each, an
     "ARCO Stock Option") which is then outstanding and unexercised shall cease
     to represent a right to acquire ARCO Common Shares and shall be converted
     automatically into an option to purchase BP Amoco Ordinary Shares, to be
     issued in the form of BP Amoco Depositary Shares, and BP Amoco shall assume
     each such ARCO Stock Option subject to the terms of the relevant ARCO Stock
     Plan, and the agreement evidencing the grant thereunder; provided, however,
     that from and after the Effective Time, (i) the number of BP Amoco Ordinary
     Shares purchasable, in the form of BP Amoco Depositary Shares, upon
     exercise of each such ARCO Stock Option shall be equal to the number of
     ARCO Common Shares that were purchasable under such ARCO Stock Option
     immediately prior to the Effective Time (without taking into account any
     Dividend Share Credits under any ARCO Stock Plan), multiplied by the
     Exchange Ratio, subject to adjustment as provided in Section 1.3.5, and
     rounding down to the nearest whole BP Amoco Ordinary Share and (ii) the per
     BP Amoco Ordinary


                                       -7-

<PAGE>



     Share exercise price under each such ARCO Stock Option shall be obtained by
     dividing the per share exercise price of each such ARCO Stock Option by the
     Exchange Ratio, subject to adjustment as provided in Section 1.3.5, and
     rounding down to the nearest cent. Notwithstanding the foregoing, the
     number of BP Amoco Ordinary Shares and the per BP Amoco Ordinary Share
     exercise price of each ARCO Stock Option which is intended to be an
     "incentive stock option" (as defined in Section 422 of the Code) shall be
     adjusted in accordance with the requirements of Section 424 of the Code.
     Accordingly, with respect to any incentive stock options, fractional BP
     Amoco Ordinary Shares shall be rounded down to the nearest whole number of
     BP Amoco Ordinary Shares and where necessary the per BP Amoco Ordinary
     Share exercise price shall be rounded up to the nearest cent. BP Amoco
     Ordinary Shares to be issued upon the exercise of ARCO Stock Options,
     shall, at the election of the holders of such ARCO Stock Options, be
     delivered in the form of BP Amoco Depositary Shares.

         1.5.2. Shares of Restricted Stock and Performance-Based Restricted
     Stock outstanding and held by participants in any ARCO Stock Plan
     immediately prior to the Effective Time shall be converted into and shall
     be canceled in exchange for the right to receive BP Amoco Shares in
     accordance with Sections 1.3.2 and 1.4.1.

         1.5.3.  The obligation of ARCO to deliver ARCO Common Shares pursuant
     to Article III, Subsection 3(b)(v)(1) of the ARCO 1985 Executive Long-Term
     Incentive Plan (the "ELTIP"), as amended through the date hereof, in
     respect of Contingent Restricted Stock upon the Change of Control
     represented by the Merger shall be satisfied through the delivery by BP
     Amoco of (i) a number of BP Amoco Ordinary Shares (to be issued in the form
     of BP Amoco Depositary Shares) equal to the number of ARCO Common Shares
     that were otherwise so deliverable multiplied by the Exchange Ratio, and
     (ii) such other amounts payable in respect of such ARCO Common Shares
     pursuant to this Article I.

         1.5.4.  With respect to Dividend Share Credits under any ARCO Stock
     Plan, including Prospective Dividend Share Credits to be credited pursuant
     to Article IV, Subsection 4(b) of the ELTIP and under Article II, Section
     2.6 of the Director's Plan (as defined in Section 1.5.6(b)) in connection
     with the Merger, BP Amoco and ARCO agree that: (a) as of the Effective
     Time, ARCO Common Shares represented by Dividend Share Credits, including
     such Prospective Dividend Share Credits, shall be deemed converted into BP
     Amoco Ordinary Shares at the Exchange Ratio; (b) after the Effective Time
     the obligation of ARCO to deliver ARCO Common Shares under Article IV,
     Section 3 of the ELTIP shall be satisfied through the delivery by BP Amoco
     of a number of BP Amoco Ordinary Shares (to be issued in the form of BP
     Amoco Depositary Shares) equal 


                                       -8-

<PAGE>



     to the number of ARCO Common Shares that were otherwise so deliverable
     multiplied by the Exchange Ratio; and (c) after the Effective Time,
     references in Article IV of the ELTIP and Article V of the Directors' Plan
     to "Common Stock" shall be deemed references to "BP Amoco Ordinary Shares",
     and references in Article I, Subsection 2(m) of the ELTIP and Article II,
     Subsection 2.7 of the Directors' Plan to "New York Stock Exchange" shall be
     to "London Stock Exchange".

         1.5.5. At the Effective Time, each right of any kind, whether vested or
     unvested, contingent or accrued, to acquire or receive ARCO Common Shares
     that may be held, awarded, outstanding, credited, payable or reserved for
     issuance under the ARCO Stock Plans and any other ARCO Compensation and
     Benefit Plan (as defined in 2.1.12), except for ARCO Stock Options
     converted in accordance with Section 1.5.1, shares of Restricted Stock and
     Performance-Based Restricted Stock converted in accordance with Section
     1.5.2, Contingent Restricted Stock converted in accordance with Section
     1.5.3, and any Dividend Share Credits converted in accordance with 1.5.4,
     shall be deemed to be converted into a right to acquire or receive, as the
     case may be, the number of BP Amoco Ordinary Shares (to be issued in the
     form of BP Amoco Depositary Shares) equal to the number of ARCO Common
     Shares subject to such right immediately prior to the Effective Time
     multiplied by the Exchange Ratio, and such rights with respect to BP Amoco
     Ordinary Shares shall otherwise be subject to the same terms, conditions
     and restrictions, if any, as were applicable to the rights with respect to
     ARCO Common Shares under the relevant ARCO Stock Plan or ARCO Compensation
     and Benefit Plan. Similarly, all ARCO Stock Plans and other ARCO
     Compensation and Benefit Plans (and awards thereunder) providing for cash
     payments measured by the value of a number of ARCO Common Shares shall be
     deemed to refer to the number of BP Amoco Ordinary Shares equal to the
     result of multiplying such number of ARCO Common Shares by the Exchange
     Ratio, and such cash payments shall otherwise be made on the same terms,
     conditions and restrictions, if any, as were applicable under the relevant
     ARCO Stock Plan or ARCO Compensation and Benefit Plan. At or prior to the
     Effective Time, ARCO shall adopt appropriate amendments to the ARCO Stock
     Plans and the ARCO Compensation and Benefit Plans to effectuate the
     provisions of this Section 1.5.5. Without limiting the applicability of the
     foregoing, ARCO shall take all necessary action to ensure that the
     Surviving Corporation will not be bound at the Effective Time by any
     options, stock appreciation rights, warrants or other rights or
     arrangements under any ARCO Compensation and Benefit Plan that would
     entitle any person to own any ARCO Common Shares or to receive any payments
     in respect thereof, and all ARCO Compensation and Benefit Plans conferring
     any rights to ARCO Common Shares or other capital stock of ARCO shall be
     deemed to be amended to be in conformity with this Section.



                                       -9-

<PAGE>



         1.5.6. (a) All capitalized terms used in this Section 1.5 and not
     otherwise defined in this Agreement shall have the respective meanings
     given such terms in the ELTIP.

               (b) "Directors' Plan" means the Stock Option Plan for Outside
     Directors of ARCO, as amended through the date hereof.

         1.5.7. Prior to the Effective Time, BP Amoco shall make available for
     issuance in accordance with Section 1.4.1 the number of BP Amoco Ordinary
     Shares necessary to satisfy BP Amoco's obligations under this Section 1.5.
     At the Effective Time, BP Amoco shall file with the Securities and Exchange
     Commission (the "SEC") a registration statement on an appropriate form or a
     post-effective amendment to a previously filed registration statement under
     the Securities Act of 1933, as amended (the "Securities Act"), (i) with
     respect to the BP Amoco Ordinary Shares and the BP Amoco Depositary Shares
     subject to issuance or subject to options pursuant to this Section 1.5, and
     (ii) if registration of any other interests in any ARCO Stock Plan or any
     other ARCO Compensation and Benefit Plan referred to in this Section 1.5,
     or the BP Amoco Ordinary Shares and BP Amoco Depositary Shares to be issued
     thereunder, is required under the Securities Act, with respect to such
     interests or such BP Amoco Ordinary Shares or BP Amoco Depositary Shares,
     BP Amoco shall use its best reasonable efforts to cause such registration
     statement to become and remain effective and maintain the current status of
     the prospectus contained therein, as well as comply with any applicable
     state securities or "blue sky" laws, for so long as such options remain
     outstanding.

         1.6. Fractional BP Amoco Shares. No fraction of a BP Amoco Share will
be issued. In lieu of any such fractional shares, each holder of ARCO Common
Shares who would otherwise be entitled to such fractional shares shall be
entitled to an amount in cash, without interest, rounded to the nearest cent,
equal to the product of (i) the amount of the fractional interest in an BP Amoco
Ordinary Share or BP Amoco Depositary Share, as the case may be, to which such
holder is entitled under Section 1.3 (or would be entitled but for this Section
1.6) and (ii) (A) in respect of fractional interests in BP Amoco Depositary
Shares, the average of the closing sale prices for the BP Amoco Depositary
Shares on the New York Stock Exchange (the "NYSE"), as reported in The Wall
Street Journal, Northeastern edition, for each of the ten consecutive trading
days ending with the fifth complete trading day prior to the Closing Date (not
counting the Closing Date) and (B) in respect of fractional interests in BP
Amoco Ordinary Shares, the average of the closing mid-market prices for the BP
Amoco Ordinary Shares on the London Stock Exchange Limited (the "LSE"), as
reported in The Financial Times, for each of the ten consecutive trading days
ending with the fifth complete trading day prior to the Closing Date (not
counting the Closing Date). As soon as practicable after the


                                      -10-

<PAGE>



determination of the amount of cash, if any, to be paid to holders of ARCO
Common Shares in lieu of any fractional interests, the Exchange Agent shall make
available such amounts to such holders without interest.

         1.7.   The Surviving Corporation.

         1.7.1. The certificate of incorporation of the Surviving Corporation
     shall be the restated certificate of incorporation of ARCO, unless this
     Agreement is adopted by the holders of 66 2/3% of the outstanding stock
     entitled to vote at the ARCO Stockholders Meeting (as defined in Section
     3.4), in which case the restated certificate of incorporation of the
     Surviving Corporation shall be amended as of the Effective Time to delete
     Articles V, VI, VII and VIII and to substitute therefor Articles V, VI and
     VII as set forth in full in Exhibit A.

         1.7.2. The bylaws of Merger Sub in effect at the Effective Time shall
     be the bylaws of the Surviving Corporation until amended in accordance with
     applicable law.

         1.7.3. From and after the Effective Time, until successors are duly
     elected or appointed and qualified in accordance with applicable law, (i)
     the directors of Merger Sub at the Effective Time shall be the directors of
     the Surviving Corporation, and (ii) such officers as are mutually agreed by
     BP Amoco and ARCO prior to the Effective Time shall be the officers of the
     Surviving Corporation.

         1.8. Lost, Stolen or Destroyed Certificates. In the event any
Certificate shall have been lost, stolen or destroyed, upon the holder's
compliance with the replacement requirements established by the Exchange Agent,
including, if necessary, the posting by such Person of a bond in customary
amount as indemnity against any claim that may be made against it with respect
to such Certificate, the Exchange Agent will issue in exchange for such lost,
stolen or destroyed Certificate, the Merger Consideration and any cash payable
in lieu of fractional BP Amoco Shares and any unpaid dividends or other
distributions deliverable pursuant to Section 1.4.6 in respect of the ARCO
Common Shares represented by such Certificate pursuant to this Agreement.


                                   ARTICLE II

                         Representations and Warranties

         2.1. Representations and Warranties of BP Amoco and ARCO. Except as set
forth in the corresponding sections or subsections of the disclosure letter,
dated the


                                      -11-

<PAGE>



date hereof and signed by an authorized officer, delivered by BP Amoco to ARCO
or by ARCO to BP Amoco (each a "Disclosure Letter," and the "BP Amoco Disclosure
Letter" and the "ARCO Disclosure Letter," respectively), as the case may be, BP
Amoco (except for Sections 2.1.2.2, 2.1.3.2, 2.1.5.2, 2.1.8, 2.1.9(ii),
2.1.10.2, 2.1.12, 2.1.14 and 2.1.15 and references in Section 2.1.1 to documents
made available by ARCO to BP Amoco) hereby represents and warrants to ARCO, and
ARCO (except for Sections 2.1.2.1, 2.1.3.1, 2.1.5.1, 2.1.9(i), 2.1.10.1 and
2.1.11 and references in Section 2.1.1 to documents made available by BP Amoco
to ARCO), subject to Section 2.2, hereby represents and warrants to BP Amoco,
that:

         2.1.1. Organization, Good Standing and Qualification. Each of it and
     its Subsidiaries (as defined below), is duly organized, validly existing
     and in good standing (with respect to jurisdictions that recognize the
     concept of good standing) under the laws of its respective jurisdiction of
     organization and has all requisite corporate or similar power and
     authority, and has been duly authorized by all necessary approvals and
     orders, to own, operate and lease its properties and assets and to carry on
     its business as presently conducted and is duly qualified to do business
     and is in good standing in each jurisdiction where the ownership, operation
     or leasing of its assets or properties or conduct of its business requires
     such qualification, except where the failure to be so organized, qualified
     or in good standing, or to have such power or authority, would not,
     individually or in the aggregate, reasonably be expected to have a Material
     Adverse Effect (as defined below) on it. BP Amoco has made available to
     ARCO complete and correct copies of its memorandum and articles of
     association, and ARCO has made available to BP Amoco complete and correct
     copies of its restated certificate of incorporation and by-laws, in all
     cases as amended to date. Such memorandum and articles of association or
     restated certificate of incorporation and by-laws, as the case may be, as
     so made available are in full force and effect.

         As used in this Agreement, the term (i) "Subsidiary" means, with
     respect to BP Amoco, any body corporate which is a subsidiary or subsidiary
     undertaking, in each case within the meaning of the Companies Act of 1985
     of the United Kingdom, as amended (the "Companies Act"), and, with respect
     to ARCO, any entity, whether incorporated or unincorporated, in which ARCO
     owns, directly or indirectly, more than fifty percent of the securities or
     other ownership interests having by their terms ordinary voting power to
     elect more than fifty percent of the directors or other persons performing
     similar functions, or the management and policies of which ARCO otherwise
     has the power to direct, (ii) "Material Adverse Effect" means, with respect
     to any Person (as defined below), a material adverse effect on the
     financial condition, properties, business or operating income of such
     Person and its Subsidiaries taken as a whole, other than any such effect to
     the extent arising out of changes in general United States, United Kingdom
     or


                                      -12-

<PAGE>



     international economic conditions, conditions or changes in or affecting
     the United States, United Kingdom or international oil and gas industry
     (including changes in market prices), provided that, except as otherwise
     specifically provided, all references to Material Adverse Effect on BP
     Amoco or any of its Subsidiaries or to ARCO or any of its Subsidiaries in
     this Article II or in Article III shall be deemed to refer solely to BP
     Amoco and its Subsidiaries and ARCO and its Subsidiaries, respectively,
     without giving effect to BP Amoco's ownership of ARCO and its Subsidiaries
     after the Effective Time, (iii) "Person" shall mean any individual,
     corporation (including not-for-profit), general or limited partnership,
     limited liability or unlimited liability company, joint venture, estate,
     trust, association, organization, Governmental Entity (as defined in
     Section 2.1.4.1) or other entity of any kind or nature, and (iv)
     "Affiliate" shall have the meaning specified in Rule 12b-2 of the
     Securities Exchange Act of 1934, as amended (the "Exchange Act").

         2.1.2. Capital Structure.

               2.1.2.1. The authorized share capital of BP Amoco is
         $6,000,000,000 and (pound)12,750,000. As of the close of business on
         March 29, 1999, the allotted share capital of BP Amoco consisted of
         9,720,380,579 BP Amoco Ordinary Shares, not more than 7,232,838 8%
         cumulative first preference shares, of nominal value (pound)1 each ("BP
         Amoco First Preference Shares"), and not more than 5,473,414 9%
         cumulative second preference shares, of nominal value (pound)1 each
         ("BP Amoco Second Preference Shares"). All of the outstanding BP Amoco
         Ordinary Shares, BP Amoco First Preference Shares and BP Amoco Second
         Preference Shares have been, and the BP Amoco Ordinary Shares to be
         issued as Merger Consideration shall be, duly authorized and validly
         issued and are or will be, as the case may be, fully paid or credited
         as fully paid. BP Amoco has no BP Amoco Ordinary Shares, BP Amoco First
         Preference Shares or BP Amoco Second Preference Shares reserved for or
         otherwise subject to issuance, except for BP Amoco Ordinary Shares held
         by trusts or otherwise subject to issuance in relation to option
         schemes pursuant to which BP Amoco Ordinary Shares may be issued in the
         ordinary course of business (the "Option Schemes"). Each of the
         outstanding shares of capital stock or other ownership interests of
         each of BP Amoco's Subsidiaries that constitutes a "Significant
         Subsidiary" (as defined in Rule 1-02(w) of Regulation S-X promulgated
         under the Exchange Act) is duly authorized, validly issued, fully paid
         and nonassessable and owned by BP Amoco or a direct or indirect wholly
         owned Subsidiary of BP Amoco, in each case free and clear of any lien,
         pledge, security interest, claim or other encumbrance ("Encumbrance").
         Except as set forth above or as contemplated by this


                                      -13-

<PAGE>



         Agreement, there are no pre-emptive or other outstanding rights,
         options, warrants, conversion rights, stock appreciation rights,
         redemption rights, repurchase rights, agreements, arrangements, calls,
         commitments or rights of any kind which obligate BP Amoco or any of its
         Subsidiaries to issue or to sell any shares of capital stock or other
         securities of BP Amoco or any of its Subsidiaries or any securities or
         obligations convertible or exchangeable into or exercisable for, or
         giving any Person a right to subscribe for or acquire from BP Amoco or
         any of its Subsidiaries, any securities of BP Amoco or any of its
         Subsidiaries, and no securities or obligations evidencing such rights
         are authorized, issued or outstanding. BP Amoco does not have
         outstanding any bonds, debentures, notes or other obligations the
         holders of which have the right to vote (or which are convertible into
         or exercisable for securities having the right to vote) with the
         shareholders of BP Amoco on any matter.

               2.1.2.2. The authorized capital stock of ARCO consists of
         600,000,000 ARCO Common Shares, of which 325,937,777 ARCO Common Shares
         were issued and outstanding as of the close of business on March 26,
         1999, 75,000,000 shares of Preferred Stock, par value $.01 per share
         ("ARCO Preferred Stock"), of which no shares were outstanding as of the
         date hereof; 78,089 shares of $3.00 Cumulative Convertible Preference
         Stock, par value $1.00 per share ("ARCO $3.00 Preference Stock"), of
         which 49,749 shares were outstanding as of March 26, 1999; and 833,776
         shares of $2.80 Cumulative Convertible Preference Stock, par value
         $1.00 per share ("ARCO $2.80 Preference Stock"), of which 564,439
         shares were outstanding as of March 26, 1999 (the ARCO $3.00 Preference
         Stock and the ARCO $2.80 Preference Stock being referred to herein as
         the "ARCO Preference Stock"). All of the outstanding ARCO Common Shares
         and shares of ARCO Preference Stock have been duly authorized and
         validly issued and are fully paid and nonassessable. ARCO has no ARCO
         Common Shares, shares of ARCO Preferred Stock or shares of ARCO
         Preference Stock reserved for or otherwise subject to issuance, except
         that (i) as of the close of business on March 29, 1999, there were
         13,927,493.16 ARCO Common Shares subject to issuance pursuant to
         options or other common stock equivalents (excluding Prospective
         Dividend Share Credits (as defined in the ELTIP)) outstanding under the
         plans of ARCO identified in paragraph 2.1.2.2 of the ARCO Disclosure
         Letter as being the only ARCO Compensation and Benefit Plans pursuant
         to which ARCO Common Shares may be issued (the "ARCO Stock Plans"); and
         (ii) as of the date hereof, there are not less than 64,861,617 ARCO
         Common Shares reserved for issuance pursuant to the Stock Option
         Agreement. Each of the outstanding shares of capital stock or


                                      -14-

<PAGE>



         other ownership interests of each of ARCO's Significant Subsidiaries
         (or, in the case of Vastar Resources, Inc. ("Vastar"), the shares of
         capital stock of Vastar owned by ARCO) is duly authorized, validly
         issued, fully paid and nonassessable and owned by ARCO or a direct or
         indirect wholly owned subsidiary of ARCO, in each case free and clear
         of any Encumbrance. Except as set forth above or as contemplated by
         this Agreement, there are no preemptive or other outstanding rights,
         options, warrants, conversion rights, stock appreciation rights,
         redemption rights, repurchase rights, agreements, arrangements, calls,
         commitments or rights of any kind which obligate ARCO or any of its
         Subsidiaries to issue or sell any shares of capital stock or other
         securities of ARCO or any of its Subsidiaries or any securities or
         obligations convertible or exchangeable into or exercisable for, or
         giving any Person a right to subscribe for or acquire from ARCO or any
         of its Subsidiaries, any securities of ARCO or any of its Subsidiaries,
         and no securities or obligations evidencing such rights are authorized,
         issued or outstanding. The ARCO Common Shares issuable pursuant to the
         Stock Option Agreement have been duly reserved for issuance by ARCO,
         and upon any issuance of such ARCO Common Shares in accordance with the
         terms of the Stock Option Agreement, such ARCO Common Shares will be
         duly authorized, validly issued, fully paid and nonassessable and free
         and clear of any Encumbrance. ARCO does not have outstanding any bonds,
         debentures, notes or other obligations the holders of which have the
         right to vote (or which are convertible into or exercisable for
         securities having the right to vote) with the stockholders of ARCO on
         any matter.

               2.1.3. Corporate Authority; Approval and Fairness.

               2.1.3.1. BP Amoco has all requisite corporate power and authority
         and has taken all corporate action necessary in order to execute,
         deliver and perform its obligations under this Agreement and the Stock
         Option Agreement and to consummate the Merger and the other
         transactions contemplated hereby and thereby, subject only to the
         approval of the Merger by, on a show of hands, not less than the
         requisite majority of the holders of outstanding BP Amoco Ordinary
         Shares, BP Amoco First Preference Shares and BP Amoco Second Preference
         Shares (collectively, the "BP Amoco Voting Shares") present in person
         or, on a poll, not less than the requisite majority of the votes
         attaching to the BP Amoco Voting Shares voted by the holders in person
         or by proxy at the BP Amoco Shareholders Meeting (as defined in Section
         3.4) (the "BP Amoco Requisite Vote"). The execution, delivery and
         performance of this Agreement and the Stock Option Agreement have been
         duly authorized by


                                      -15-

<PAGE>



         all necessary corporate action on the part of BP Amoco, and, assuming
         the due authorization, execution and delivery of this Agreement and the
         Stock Option Agreement by ARCO, this Agreement and the Stock Option
         Agreement constitute valid and binding agreements of BP Amoco,
         enforceable against BP Amoco in accordance with their terms, subject to
         bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium
         and similar laws of general applicability relating to or affecting
         creditors' rights and to general equity principles (the "Bankruptcy and
         Equity Exception"). The Board of Directors of BP Amoco has approved
         this Agreement, the Stock Option Agreement, the Merger and the other
         transactions contemplated hereby and thereby and the Board of Directors
         has received the opinion of its financial advisor, Morgan Stanley & Co.
         Incorporated, to the effect that, as of the date of this Agreement, the
         Exchange Ratio is fair to BP Amoco, from a financial point of view.

               2.1.3.2. ARCO has all requisite corporate power and authority and
         has taken all corporate action necessary in order to execute, deliver
         and perform its obligations under this Agreement and the Stock Option
         Agreement and to consummate the Merger and the other transactions
         contemplated hereby and thereby, subject only to the adoption of this
         Agreement by the vote of the holders of a majority of the outstanding
         stock entitled to vote at the ARCO Stockholders Meeting (as defined in
         Section 3.4) (the "ARCO Requisite Vote"). The execution, delivery and
         performance of this Agreement and the Stock Option Agreement have been
         duly authorized by all necessary corporate action on the part of ARCO
         and, assuming the due authorization, execution and delivery of this
         Agreement and the Stock Option Agreement by BP Amoco, this Agreement
         and the Stock Option Agreement constitute valid and binding agreements
         of ARCO enforceable against ARCO in accordance with their terms,
         subject to the Bankruptcy and Equity Exception. The Board of Directors
         of ARCO (A) has unanimously approved this Agreement, the Stock Option
         Agreement, the Merger and the other transactions contemplated hereby
         and thereby and declared the advisability of the Merger Agreement and
         (B) has received the opinions of its financial advisors, Goldman, Sachs
         & Co. and Salomon Smith Barney Inc., to the effect that, as of the date
         of this Agreement, the Exchange Ratio is fair to the holders of ARCO
         Common Shares (other than holders of Excluded ARCO Shares) from a
         financial point of view.



                                      -16-

<PAGE>



               2.1.4. Governmental Filings; No Violations.

               2.1.4.1. Other than the necessary filings, permits,
         authorizations, notices, approvals, confirmations, consents,
         declarations and/or decisions (A) pursuant to Sections 1.2.2 and 3.3.1,
         (B) under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
         amended (the "HSR Act"), the Exchange Act, the Securities Act and the
         Exon-Florio provisions of the Omnibus Trade and Competitiveness Act of
         1988 ("Exon-Florio"), (C) to comply with the rules and regulations of
         the NYSE or the LSE or any other stock exchanges on which securities of
         BP Amoco, ARCO or any of their respective Subsidiaries are listed, (D)
         to comply with Council Regulation (EEC) No 4064/89 as amended (the
         "Regulation"), (insofar as the Merger constitutes a concentration with
         a Community dimension within the scope of the Regulation), (E) from the
         UK Office of Fair Trading that is not the intention of the UK Secretary
         of State for Trade and Industry to refer the Merger or any matters
         arising therefrom to the UK Monopolies and Mergers Commission (the
         "MMC") or from the Secretary of State for Trade and Industry in the
         event that the Merger or any matters arising therefrom are referred to
         the MMC (insofar as the Merger qualifies for investigation by the MMC
         under the UK Fair Trading Act 1973 or a referral is made by the
         European Commission to the UK Competent Authority under Article 9 of
         the Regulation), (F) with or from any other national authority within
         the European Community to which the Merger (or any part of it) is
         referred pursuant to Article 9 of the Regulation) and (G) from H.M.
         Treasury pursuant to section 765 of the Income and Corporation Taxes
         Act 1988 (or the confirmation from H.M. Treasury or the Inland Revenue
         that no such consent is required to the transactions contemplated by
         this Agreement) (such filings, permits, authorizations, notices,
         approvals, confirmations, consents, declarations and/or decisions to be
         made, given or obtained by BP Amoco being the "BP Amoco Required
         Consents" and by ARCO being the "ARCO Required Consents"), no filings,
         notices, declarations and/or decisions are required to be made by it
         with, nor are any permits, authorizations, approvals or other
         confirmations or consents required to be obtained by it from, any
         governmental or regulatory (including stock exchange) authority,
         agency, court, commission, body or other governmental entity (including
         the U.K. Panel on Takeovers and Mergers (the "Takeover Panel")) (each,
         a "Governmental Entity"), in connection with the execution and delivery
         by it of this Agreement and the Stock Option Agreement and the
         consummation by it of the Merger and the other transactions
         contemplated hereby and thereby, except those the failure of which to
         make, give or obtain would not, individually or in the aggregate,
         reasonably be expected to have a 


                                      -17-

<PAGE>



         Material Adverse Effect on it or prevent, materially delay or
         materially impair its ability to consummate the Merger and the other
         transactions contemplated by this Agreement and the Stock Option
         Agreement.

               2.1.4.2.  The execution, delivery and performance of this
         Agreement and the Stock Option Agreement by it do not, and the
         consummation by it of the Merger and the other transactions
         contemplated hereby and thereby (including, in the case of BP Amoco,
         the issue of BP Amoco Ordinary Shares, and the deposit of BP Amoco
         Ordinary Shares by or on behalf of BP Amoco with the Depositary against
         issuance of BP Amoco Depositary Shares in accordance with the Deposit
         Agreement) will not, constitute or result in (A) a breach or violation
         of, or a default under, its memorandum or articles of association, in
         the case of BP Amoco, or its restated certificate of incorporation or
         by-laws, in the case of ARCO, or the comparable governing instruments
         of any of the Significant Subsidiaries of BP Amoco or ARCO (in each
         case as amended from time to time), (B) subject to making, giving or
         obtaining all necessary filings, permits, authorizations, notices,
         approvals, confirmations, consents, declarations and/or decisions
         described in Section 2.1.4.1 and all other necessary third-party
         consents as set forth in paragraph 2.1.4.2 of its Disclosure Letter, a
         breach or violation of, or a default under, the acceleration of any
         obligations or rights of third parties or the creation of an
         Encumbrance on the assets of it or any of its Subsidiaries (with or
         without notice, lapse of time or both) pursuant to any agreement,
         lease, license, contract, note, mortgage, indenture, arrangement or
         other obligation ("Contracts") binding upon it or any of its
         Subsidiaries or any law, ordinance, regulation, judgment, order,
         decree, arbitration, award, license or permit of any Governmental
         Entity ("Law") or non-governmental permit or license to which it or any
         of its Subsidiaries is subject, or (C) any change in the rights or
         obligations of either Party under any of its Contracts, except, in the
         case of clause (B) or (C) above, for any breach, violation, default,
         acceleration, creation or change that, individually or in the
         aggregate, would not reasonably be expected to have a Material Adverse
         Effect on it or prevent, materially delay or materially impair its
         ability to consummate the Merger and the other transactions
         contemplated by this Agreement and the Stock Option Agreement.

         2.1.5. Reports; Financial Statements.

                  2.1.5.1. BP Amoco has made available to ARCO copies of (A)
            each registration statement, report and annual report prepared by it
            or its Subsidiaries and filed with the SEC since December 31, 1997,
            each in the

                                 -18-

<PAGE>



         form (including exhibits, annexes and any amendments thereto) filed
         with the SEC, a draft as of the date hereof of BP Amoco's Annual Report
         on Form 20-F for the year ended December 31, 1998 (the "BP Amoco 20-F,"
         December 31, 1998 being the "BP Amoco Audit Date"), and each quarterly
         report distributed by BP Amoco to its shareholders (collectively,
         including any such registration statement, report or annual report
         filed with the SEC or, in the case of quarterly reports, distributed to
         BP Amoco shareholders subsequent to the date hereof, the "BP Amoco
         Reports"); and (B) all circulars, reports and other documents
         distributed by BP Amoco to its shareholders since the BP Amoco Audit
         Date. As of their respective dates, the BP Amoco Reports (i) complied
         in all material respects with, and any BP Amoco Report filed,
         distributed or delivered subsequent to the date hereof will comply in
         all material respects with, any applicable requirements of the
         Securities Act and the Exchange Act and the rules and regulations of
         the SEC promulgated thereunder and (ii) did not, and any BP Amoco
         Report filed, distributed or delivered subsequent to the date hereof
         will not (and all circulars, reports and other documents referred to in
         clause (B) of the preceding sentence did not, and such materials
         circulated subsequent to the date hereof will not), contain any untrue
         statement of a material fact or omit to state a material fact required
         to be stated therein or necessary to make the statements made therein,
         in the light of the circumstances under which they were made, not
         misleading. Each of the audited consolidated balance sheets of BP Amoco
         and its Subsidiaries included in or incorporated by reference into the
         BP Amoco Reports (including the related notes and schedules) fairly
         presents, or will fairly present, in all material respects, the
         consolidated financial position of BP Amoco and its Subsidiaries as of
         its date, and each of the related consolidated statements of income,
         changes in shareholders' interest, total recognized gains and losses
         and cash flows included in or incorporated by reference into the BP
         Amoco Reports (including any related notes and schedules) fairly
         presents, or will fairly present, in all material respects, the
         consolidated results of its operations, retained earnings and cash
         flows of BP Amoco and its Subsidiaries as of the relevant dates for the
         periods set forth therein (subject, in the case of unaudited
         statements, to notes and normal year-end audit adjustments that will
         not be material in amount or effect), in each case in accordance with
         generally accepted accounting principles in the U.K. ("U.K. GAAP")
         consistently applied during the periods involved except as may be noted
         therein. The related notes reconciling to generally accepted accounting
         principles in the United States ("U.S. GAAP") the consolidated net
         income and shareholders' equity of BP Amoco and its Subsidiaries comply
         in all material respects with the requirements of the SEC applicable to
         such reconciliation.


                                      -19-

<PAGE>




               2.1.5.2. ARCO has made available to BP Amoco copies of each
         registration statement, report, proxy statement or information
         statement prepared by it or any of its Subsidiaries and filed with the
         SEC since December 31, 1998 (December 31, 1998 being the "ARCO Audit
         Date," with the BP Amoco Audit Date and the ARCO Audit Date each being
         referred to herein as the relevant Party's "Audit Date"), including
         ARCO's Annual Report on Form 10-K for the year ended December 31, 1998,
         each in the form (including exhibits, annexes and any amendments
         thereto) filed with the SEC (collectively, including any such
         registration statement, report, proxy statement or information
         statement filed with the SEC subsequent to the date hereof, the "ARCO
         Reports"). As of their respective dates, the ARCO Reports (i) complied
         in all material respects with, and any ARCO Report filed subsequent to
         the date hereof will comply in all material respects with, any
         applicable requirements of the Securities Act and the Exchange Act and
         the rules and regulations of the SEC promulgated thereunder and (ii)
         did not, and any ARCO Reports filed with the SEC subsequent to the date
         hereof will not, contain any untrue statement of a material fact or
         omit to state a material fact required to be stated therein or
         necessary to make the statements made therein, in the light of the
         circumstances under which they were made, not misleading. Each of the
         consolidated balance sheets included in or incorporated by reference
         into the ARCO Reports (including the related notes and schedules)
         fairly presents, or will fairly present, in all material respects, the
         consolidated financial position of ARCO and its Subsidiaries as of its
         date and each of the related consolidated statements of income, changes
         in stockholders' equity and cash flows included in or incorporated by
         reference into the ARCO Reports (including any related notes and
         schedules) fairly presents, or will fairly present in all material
         respects, the consolidated results of operations and cash flows of ARCO
         and its Subsidiaries for the periods set forth therein (subject, in the
         case of unaudited statements, to notes and normal year-end audit
         adjustments that will not be material in amount or effect), in each
         case in accordance with U.S. GAAP consistently applied during the
         periods involved except as may be noted therein. The BP Amoco Reports
         and the ARCO Reports are collectively referred to herein as the
         "Reports," and references in this Agreement to "Reports filed prior to
         the date hereof" shall include, with respect to BP Amoco, the BP Amoco
         20-F provided to ARCO on or prior to the date hereof.

         2.1.6. Absence of Certain Changes. Except as disclosed in the Reports
     filed prior to the date hereof, or as expressly contemplated by this
     Agreement, since its respective Audit Date it and its Subsidiaries have
     conducted their


                                      -20-

<PAGE>



     respective businesses only in, and have not engaged in any material
     transaction other than according to, the ordinary and usual course of such
     businesses, and there has not been (i) any change in the financial
     condition, properties, business or operating income of it and its
     Subsidiaries except those changes that, individually or in the aggregate,
     have not had and would not reasonably be expected to have a Material
     Adverse Effect on it; (ii) any declaration, setting aside or payment of any
     dividend or other distribution in cash, stock or property in respect of its
     capital stock, except for dividends or other distributions on its capital
     stock publicly announced prior to the date hereof and except as expressly
     permitted hereby; (iii) any stock split, stock combination,
     recapitalization, redenomination of share capital or other similar
     transaction or issuance or authorization of any issuance of any other
     securities in respect of, in lieu of or in substitution for shares of its
     capital stock, except as expressly contemplated hereby or, in the case of
     ARCO, in the Stock Option Agreement; or (iv) any change by it in accounting
     principles, practices or methods except as required by changes in U.K. GAAP
     or U.S. GAAP, as the case may be. Since its respective Audit Date, except
     as provided for herein or as disclosed in the Reports filed prior to the
     date hereof, there has not been any material increase in the compensation
     payable or that could become payable by it or any of its Subsidiaries to
     officers or key employees or any amendment of any of its compensation or
     benefit plans or agreements other than increases or amendments in the
     ordinary course or as contemplated by this Agreement.

         2.1.7. Litigation and Liabilities. Except as disclosed in the Reports
     filed prior to the date hereof, there are no (i) civil, criminal or
     administrative actions, suits, claims, hearings, investigations, complaints
     or proceedings pending or, to the knowledge of, in the case of BP Amoco,
     its Chief Executive Officer, Deputy Chief Executive Officer, Chief
     Financial Officer or General Counsel ("BP Amoco Executive Directors"), and,
     in the case of ARCO, its Chief Executive Officer, President, Chief
     Financial Officer or General Counsel ("ARCO Executive Officers"),
     threatened against it or any of its Affiliates or (ii) obligations or
     liabilities, whether or not accrued, contingent or otherwise and whether or
     not required to be disclosed, or any other facts or circumstances of which,
     in the case of BP Amoco, the BP Amoco Executive Directors, and, in the case
     of ARCO, the ARCO Executive Officers, have knowledge that would reasonably
     be expected to result in any claims against, or obligations or liabilities
     of, it or any of its Subsidiaries, except, in each case, for those that,
     individually or in the aggregate, have not had and would not reasonably be
     expected to have a Material Adverse Effect on it or prevent, materially
     delay or materially impair its ability to consummate the Merger and the
     other transactions contemplated by this Agreement and the Stock Option
     Agreement.


                                 -21-

<PAGE>



         2.1.8. Takeover Statutes. Assuming that BP Amoco's representation and
     warranty set forth in Section 2.1.10.1 is true and correct, the board of
     directors of ARCO has taken or will take all appropriate and necessary
     action such that BP Amoco will not be prohibited from entering in a
     "business combination" with ARCO as an "interested stockholder" (in each
     case as such term is used in Section 203 of the DGCL) without complying
     with Section 203(a)(3) of the DGCL as a result of the execution and
     delivery of this Agreement and the Stock Option Agreement or the
     consummation of the transactions contemplated hereby and thereby. No other
     "fair price," "moratorium," "control share acquisition" or other similar
     anti-takeover statute or regulation, including such business combination
     provisions of the DGCL (each, a "Takeover Statute"), and no anti-takeover
     provision in the restated certificate of incorporation or by-laws of ARCO
     is, or at the Effective Time will be, applicable to the Merger or any of
     the other transactions contemplated by this Agreement and the Stock Option
     Agreement.

         2.1.9. Brokers and Finders. Neither it nor any of its Subsidiaries,
     officers, directors or employees has employed any broker or finder or
     incurred any liability for any brokerage fees, commissions or finders' fees
     in connection with the execution and delivery of this Agreement, the Stock
     Option Agreement, the Merger or the other transactions contemplated by this
     Agreement and the Stock Option Agreement, except that (i) BP Amoco has
     employed Morgan Stanley & Co. Incorporated, Merrill Lynch, Pierce, Fenner &
     Smith Incorporated and Cazenove & Co. as its financial advisors, the
     arrangements with all of which have been disclosed to ARCO prior to the
     date hereof, and (ii) ARCO has retained Goldman, Sachs & Co. and Salomon
     Smith Barney Inc. as its financial advisors, the arrangements with both of
     which have been disclosed to BP Amoco prior to the date hereof.

         2.1.10. Ownership of Other Party's Common Stock.

                    2.1.10.1. Neither BP Amoco nor any of its Subsidiaries
               "beneficially owns" (as such term is defined in Rule 13d-3 under
               the Exchange Act) any ARCO Common Shares.

                    2.1.10.2. Neither ARCO nor any of its Subsidiaries
               "beneficially owns" (as such term is defined in Rule 13d-3 under
               the Exchange Act) any BP Amoco Ordinary Shares or BP Amoco
               Depositary Shares (other than any BP Amoco Ordinary Shares or BP
               Amoco Depositary Shares beneficially owned by an ARCO
               Compensation and Benefit Plan or an ARCO sponsored non-U.S.
               employee benefit plan).


                                 -22-

<PAGE>



               2.1.11. Merger Sub. Merger Sub was formed solely for the purpose
         of engaging in the transactions contemplated hereby and has not (i)
         engaged in any business activities, (ii) conducted any operations other
         than in connection with the transactions contemplated hereby or (iii)
         incurred any liabilities other than in connection with the transactions
         contemplated hereby. The execution, delivery and performance of this
         Agreement have been duly authorized by all necessary corporate action
         on the part of Merger Sub and, assuming the due authorization,
         execution and delivery of this Agreement by ARCO and BP Amoco, this
         Agreement constitutes a valid and binding agreement of Merger Sub
         enforceable against Merger Sub in accordance with its terms, subject to
         the Bankruptcy and Equity Exception. BP Amoco, as Merger Sub's sole
         stockholder, has approved Merger Sub's execution, delivery and
         performance of this Agreement and has adopted this Agreement.

               2.1.12. ARCO Employee Benefit Plans.

                    2.1.12.1. Set forth in Section 2.1.12 of the ARCO Disclosure
               Letter are all significant compensation and benefit plans,
               contracts, policies or arrangements currently in effect for U.S.
               based employees covering current or former employees of ARCO and
               its Subsidiaries and current or former directors of ARCO,
               including, but not limited to, "employee benefit plans" within
               the meaning of Section 3(3) of the Employee Retirement Income
               Security Act of 1974, as amended ("ERISA"), and deferred
               compensation, stock option, stock purchase, stock appreciation
               rights, stock based, incentive and bonus plans (the "ARCO
               Compensation and Benefit Plans"). True and complete copies of all
               ARCO Compensation and Benefit Plans, including, but not limited
               to, any trust instruments and insurance contracts forming a part
               of any ARCO Compensation and Benefit Plan, and all amendments
               thereto have been provided or made available to BP Amoco.

                    2.1.12.2. Except as set forth in Section 2.1.12 of the ARCO
               Disclosure Letter, none of the execution and delivery of this
               Agreement by ARCO, the performance by ARCO of its obligations
               hereunder, the consummation of the transactions contemplated by
               this Agreement nor any other action taken or failed to be taken
               by ARCO prior to the execution of this Agreement will (a) limit
               ARCO's right, in its sole discretion, to administer, amend or
               terminate any ARCO Compensation and Benefit Plan or any related
               trust instrument, (b) entitle any employees of ARCO or any of its
               Subsidiaries to severance pay, (c) accelerate the time of payment
               or vesting or trigger any payment or funding (through a grantor
               trust or otherwise) of compensation, benefits or awards under,
               increase the amount


                                      -23-

<PAGE>



               payable or trigger any other material obligation pursuant to, any
               of the ARCO Compensation and Benefit Plans or (d) result in any
               breach or violation of, or a default under, any of the ARCO
               Compensation and Benefit Plans.

               2.1.13. Environmental Matters. Except as disclosed in its Reports
         filed prior to the date hereof and except for such matters that,
         individually or in the aggregate, have not had and would not reasonably
         be expected to have a Material Adverse Effect on it, to the knowledge
         of the BP Amoco Executive Officers or the ARCO Executive Officers, as
         applicable, (i) it and its Subsidiaries are in compliance with all
         applicable Environmental Laws; (ii) no property currently or formerly
         owned or operated by it or its Subsidiaries is contaminated with any
         Hazardous Substance requiring remediation under any Environmental Law;
         (iii) neither it nor any of its Subsidiaries is subject to liability
         under any Environmental Law for off-site disposal or contamination;
         (iv) neither it nor any of its Subsidiaries has received any claim,
         notice, demand or letter indicating that it may be in violation of, or
         subject to liability under, any Environmental Law; (v) neither it nor
         any of its Subsidiaries is subject to any order, decree, investigation,
         injunction or agreement with any Governmental Entity or any third party
         relating to any Environmental Law; and (vi) there are no other
         circumstances or conditions involving it or any of its Subsidiaries
         that reasonably could be expected to result in any claims, liabilities
         or costs in connection with any Environmental Law.

               As used herein, "Environmental Law" means any federal, state,
         local and foreign law, regulation, order, decree, common law or agency
         requirement relating to the protection of the environment or human
         health and safety, and "Hazardous Substance" means any substance, waste
         or byproduct in any concentration that is listed, classified or
         regulated pursuant to any Environmental Law, including petroleum and
         petroleum products and wastes, mine tailings and wastes, asbestos, lead
         products and polychlorinated biphenyls.

               2.1.14. ARCO Rights Plan. Assuming that BP Amoco's representation
         and warranty set forth in Section 2.1.10.1 is true and correct, the
         board of directors of ARCO has taken all action necessary to render the
         rights (the "Rights") issued under the Rights Agreement, dated as of
         July 24, 1995 (the "Rights Agreement"), between ARCO and First Chicago
         Trust Company of New York inapplicable to the Merger, this Agreement,
         the Stock Option Agreement and the other transactions contemplated
         hereby and thereby. ARCO will take all necessary action with respect to
         all of the outstanding Rights so that, as of immediately prior to the
         Effective Time, (A) neither ARCO nor BP Amoco will have any obligations
         under the Rights or the Rights Agreement and (B) the holders of the
         Rights will have no rights under the Rights or the Rights Agreement.


                                 -24-

<PAGE>



               2.1.15. ARCO Joint Ventures; Exclusivity Arrangements. For
         purposes of this Agreement, the material organizational documents,
         shareholder, membership or voting agreements and material agreements
         relating to the transfer of investments and management or operatorships
         to which it or any of its Subsidiaries is a party in connection with
         its joint ventures are referred to herein as the "Joint Venture
         Agreements", and the non-compete, exclusivity or similar agreements
         pursuant to which the ability of ARCO or any of its Subsidiaries or
         Affiliates of any of them to engage in any line of business, to
         contract with third parties or to do business in any geographic area is
         restricted in any material manner, and any area-of-mutual-interest
         agreements, are referred to herein as the "Exclusivity Agreements". All
         of ARCO's Joint Venture Agreements and Exclusivity Agreements are, with
         respect to it and its Subsidiaries, valid and in full force and effect
         on the date hereof except for any failures to be in full force and
         effect that, individually or in the aggregate, would not reasonably be
         expected to have a Material Adverse Effect on it. Neither ARCO nor any
         of its Subsidiaries has violated any provision of, or committed or
         failed to perform any act which with or without notice, lapse of time
         or both would constitute a default under the provisions of, any of its
         Joint Venture Agreements or Exclusivity Agreements, except in each case
         for such violations, acts or omissions as, individually or in the
         aggregate, would not reasonably be expected to result in a Material
         Adverse Effect on it; it being understood that no effect arising out of
         the execution, performance or consummation of this Agreement shall be
         deemed to have a Material Adverse Effect for purposes of this Section
         2.1.15.

               2.1.16. Tax Matters. Neither it nor any of its Affiliates has
         taken or agreed to take any action that would, or failed to take any
         action the omission of which would, or has reason to believe that any
         conditions exist that could reasonably be expected to (i) prevent or
         impede the Merger from qualifying as a reorganization under Section
         368(a) of the Code or (ii) cause the Eligible ARCO Shareholders to
         recognize taxable gain with respect to the Merger pursuant to Section
         367(a) of the Code (except with respect to cash received in lieu of
         fractional BP Amoco Shares).

         2.2. Vastar. Notwithstanding anything to the contrary in this Article
II, ARCO does not make any representation or warranty with respect to Vastar and
its Subsidiaries (i) as of any date after the date hereof or (ii) for matters
covered by the fifth sentence of Section 2.1.2.2, clauses (B) and (C) of Section
2.1.4.2, the last sentence of Section 2.1.6, and Section 2.1.12; provided,
however, that (x) ARCO represents and warrants as of the date hereof that, to
the knowledge of the ARCO Executive Officers, without any investigation or
inquiry, the representations and warranties referred to in the foregoing clause
(ii) are true and accurate with respect to Vastar and its Subsidiaries and (y)
ARCO will make the representations and warranties contained in Sections 2.1.5.2
and



                                      -25-

<PAGE>



2.1.6(i) with respect to Vastar and its Subsidiaries as of the Closing Date as
though made on the Closing Date (except that any such representation or warranty
that by its terms expressly speaks as of an earlier date shall be true and
correct as of its date) for purposes of Section 4.2.1.


                                   ARTICLE III

                                    Covenants

         3.1.   Interim Operations.

         3.1.1. Interim Operations of BP Amoco. BP Amoco covenants and agrees as
     to itself and its Subsidiaries that, after the date hereof and until the
     Effective Time (unless ARCO shall otherwise approve in writing and except
     as otherwise expressly contemplated by or provided in this Agreement
     (including the BP Amoco Disclosure Letter), or as required by applicable
     Law):

               3.1.1.1. BP Amoco shall not:

                    (i) amend its memorandum and articles of association in any
          manner that would adversely affect the rights of any Party under this
          Agreement, the transactions contemplated hereby or the rights of
          holders of BP Amoco Ordinary Shares or BP Amoco Depositary Shares;

                    (ii) split, combine, subdivide or reclassify its outstanding
          shares of capital stock;

                    (iii) declare, set aside or pay any dividend or distribution
          payable in cash, stock or property in respect of any capital stock
          other than (A) regular quarterly cash dividends on BP Amoco Ordinary
          Shares consistent with past practice, including periodic dividend
          increases consistent with past practice, and (B) regular cash
          dividends on the issued and outstanding BP Amoco First Preference
          Shares and BP Amoco Second Preference Shares; or

               (iv) repurchase, redeem or otherwise acquire, or permit any of
          its Subsidiaries to purchase, redeem or otherwise acquire (except for
          repurchases, redemptions or acquisitions (A) required by the terms of
          its capital stock or securities outstanding on the date hereof or (B)
          required by or in connection with the respective terms as of the date
          hereof of any Option Schemes or any dividend reinvestment plan as in
          effect on the date



                                 -26-

<PAGE>



          hereof in the ordinary course of the operation of such plans) any
          shares of the capital stock of BP Amoco or any securities convertible
          into or exchangeable or exercisable for any shares of the capital
          stock of BP Amoco;

               3.1.1.2. neither BP Amoco nor any of its Subsidiaries shall
          issue, sell, pledge, dispose of or encumber any shares of, or
          securities convertible into or exchangeable or exercisable for, or
          rights, options, warrants, conversion rights, stock appreciation
          rights, redemption rights, repurchase rights, agreements,
          arrangements, calls, commitments or rights of any kind to acquire, the
          capital stock of BP Amoco of any class (other than (x) BP Amoco
          Ordinary Shares issuable or transferable pursuant to (A) options
          outstanding on the date hereof under the Option Schemes and (B)
          additional options or rights to acquire BP Amoco Ordinary Shares
          granted under the terms of any Option Scheme as in effect on the date
          hereof or as amended, or any similar option scheme adopted in
          replacement of or as an enhancement to any such option scheme, in each
          case in the ordinary course of the operation of such option scheme,
          (y) BP Amoco Ordinary Shares issuable or transferable pursuant to such
          options or rights so granted and (z) issuances of securities in
          connection with grants, awards or issuances of stock-based
          compensation);

               3.1.1.3. subject to the provisions of Section 3.5.1, neither BP
          Amoco nor any of its Subsidiaries shall take any action or omit to
          take any action for the purpose of preventing, delaying or impeding
          the consummation of the Merger or the other transactions contemplated
          by this Agreement and the Stock Option Agreement including any action
          or omission that would cause (i) the Merger to fail to qualify as a
          reorganization under Section 368(a) of the Code or (ii) the exchange
          of BP Amoco Shares for ARCO Common Shares in the Merger to fail to
          qualify for nonrecognition of gain (except with respect to (a) cash
          received in lieu of fractional BP Amoco Shares or (b) stockholders of
          ARCO that are not Eligible ARCO Shareholders); and

               3.1.1.4. neither BP Amoco nor any of its Subsidiaries shall
          authorize or enter into an agreement to do any of the foregoing.

               3.1.2.  Interim Operations of ARCO. ARCO covenants and agrees as
          to itself and its Subsidiaries that, after the date hereof and until
          the Effective Time (unless BP Amoco shall otherwise approve in writing
          and except as otherwise expressly contemplated by or provided in this
          Agreement (including the ARCO


                                 -27-

<PAGE>



          Disclosure Letter) or the Stock Option Agreement, or as required by
          applicable Law, and subject to Section 3.17):

               3.1.2.1. the business of ARCO and its Subsidiaries shall be
          conducted in the ordinary and usual course and, to the extent
          consistent therewith, ARCO and each of its Subsidiaries shall use
          their respective best reasonable efforts to preserve its business
          organization intact and maintain its existing relations, status and
          goodwill with customers, suppliers, creditors, state, federal and
          foreign governmental authorities, lessors, employees and business
          associates;

               3.1.2.2. ARCO shall not:

                    (i) amend its restated certificate of incorporation; amend
          its by-laws in any manner that would adversely affect the rights of
          any Party under this Agreement or the transactions contemplated hereby
          or affect the rights of holders of ARCO Common Shares; or, subject to
          the fiduciary duties of ARCO's board of directors, amend, modify or
          terminate the Rights Agreement;

                    (ii) split, combine, subdivide or reclassify its outstanding
          shares of capital stock;

                    (iii) declare, set aside or pay any dividend or distribution
          payable in cash, stock or property in respect of any capital stock
          other than (A) regular quarterly cash dividends on ARCO Common Shares
          not in excess of the quarterly cash dividends declared by ARCO in the
          quarter ended December 31, 1998 and (B) regular cash dividends on the
          issued and outstanding shares of ARCO Preference Stock; or

                    (iv) repurchase, redeem or otherwise acquire, or permit any
          of its Subsidiaries to purchase, redeem or otherwise acquire (except
          for repurchases, redemptions or acquisitions (A) required by the terms
          of its capital stock or securities outstanding on the date hereof or
          (B) required by or in connection with the respective terms as of the
          date hereof of any ARCO Stock Plans or any dividend reinvestment plan
          as in effect on the date hereof in the ordinary course of the
          operation of such plans) any shares of the capital stock of ARCO or
          any securities convertible into or exchangeable or exercisable for any
          shares of the capital stock of ARCO;



                                 -28-

<PAGE>



               3.1.2.3. neither ARCO nor any of its Subsidiaries shall:

                    (i) issue, sell, pledge, dispose of or encumber any shares
          of, or securities convertible into or exchangeable or exercisable for,
          or rights, options, warrants, conversion rights, stock appreciation
          rights, redemption rights, repurchase rights, agreements,
          arrangements, calls, commitments or rights of any kind to acquire, the
          capital stock of ARCO of any class (other than (A) ARCO Common Shares
          issuable or deliverable (x) pursuant to options outstanding on the
          date hereof under the ARCO Stock Plans, (y) in connection with the
          conversion of shares of ARCO Preference Stock in accordance with their
          terms or (z) pursuant to the Stock Option Agreement; (B) issuances of
          ARCO Common Shares, including Restricted Stock, Performance-Based
          Restricted Stock, Contingent Restricted Stock and Dividend Share
          Credits, in connection with grants and awards made prior to the date
          hereof; (C) issuances of securities in connection with grants, awards
          or issuances of stock-based compensation made in accordance with
          Section 3.1.2.4; (D) Rights issuable pursuant to the Rights Agreement
          in respect of ARCO Common Shares issued or to be issued in accordance
          with this clause (i) or Section 3.1.2.4; or (E) ARCO Common Shares
          issuable upon the exercise of Rights);

                    (ii) transfer, lease, license, sell or otherwise dispose of
          any of its property or assets (including capital stock of any of its
          Subsidiaries), including any contribution of property or assets to a
          joint venture (including any joint venture that may be entered into
          pursuant to Section 3.1.2.3 (vii)) and any transfer or disposition in
          connection with financing transactions, other than property or assets
          having an aggregate fair market value of not more than $500 million;
          provided, however, that ARCO shall not transfer, lease, license, sell
          or otherwise dispose of any individual property or asset with a fair
          market value in excess of $50 million without first consulting with BP
          Amoco;

                    (iii) incur any indebtedness except for (x) long-term
          indebtedness not in excess of $1.5 billion incurred in connection with
          the refinancing of existing indebtedness and (y) commercial paper and
          short-term indebtedness repayable upon less than 30 days' notice
          without penalty (other than LIBOR "breakage" costs); provided,
          however, that ARCO shall provide reasonable advance notice to and
          consult with BP Amoco on the development of, and any proposed changes
          in, ARCO's plans for such refinancings contemplated by clause (x)
          (including expected maturities and other material terms);


                                 -29-

<PAGE>


                    (iv) make capital expenditures in an aggregate amount in
          excess of $2.7 billion during 1999 and $2.7 billion during 2000, plus,
          in each year no more than an additional 15% of such limit, after
          reasonable advance notice to and consultation with BP Amoco with
          respect to ARCO's plans for such additional capital expenditures; or,
          without first consulting with BP Amoco, authorize or commit to any
          individual future capital expenditure in an amount in excess of $50
          million unless such consultation would be inconsistent with applicable
          Laws;

                    (v) by any means make or authorize or commit to any
          acquisition of, or investment in, assets or stock of any other Person
          or entity except to the extent that such acquisition or investment is
          a capital expenditure permitted pursuant to Section 3.1.2.3(iv) or a
          contribution to a joint venture permitted pursuant to Section
          3.1.2.3(ii);

                    (vi) terminate any existing line of business; or

                    (vii) without reasonable advance notice to and consultation
          with BP Amoco, enter into any new shareholder, membership or voting
          agreements or other agreements relating to the transfer of investments
          or management or operatorships in connection with joint ventures other
          than any such agreements with respect to which the total book value or
          fair market value (whichever is greater) of all of the assets of ARCO
          and its Subsidiaries to be employed in or subject to the relevant
          joint venture is less than $200 million;

                  3.1.2.4.  neither ARCO nor any of its Subsidiaries shall

                    (i) terminate, establish, adopt, enter into, make any new
          (or accelerate or otherwise modify any existing) grants or awards of
          stock-based compensation or other benefits under, amend or otherwise
          modify any ARCO Compensation and Benefit Plan except for (A) grants or
          awards to directors, officers and employees of it or any of its
          Subsidiaries under existing ARCO Compensation and Benefit Plans in the
          ordinary and usual course of business consistent with past practice
          (which shall include normal periodic performance reviews and the
          making of related grants and awards with provisions consistent with
          past practice; but shall not include any grants or awards that would
          accelerate, vest or become payable solely as a result of the
          consummation of the transactions contemplated by this Agreement) and,
          with respect to stock-based compensation, in any event not in excess
          of a number of grants or awards (x) granted after the date of this
          Agreement and before December 31, 1999 that would (currently or



                                      -30-

<PAGE>



          with the passage of time or the fulfillment of conditions), in the
          aggregate, entitle the holders thereof to receive or to purchase
          200,000 ARCO Common Shares pursuant to at-market stock options; and
          (y) granted after February 1, 2000 that would (currently or with the
          passage of time or the fulfillment of conditions), in the aggregate,
          entitle the holders thereof to receive or to purchase 1.5 million ARCO
          Common Shares pursuant to at-market stock options and 250,000 ARCO
          Common Shares pursuant to other equity-based awards, except that
          additional stock options may be substituted for other equity-based
          awards on an equivalent value basis, with calculation of the value of
          each equity instrument based on reasonable and customary valuation
          methods; (B) actions necessary to satisfy existing contractual
          obligations under ARCO Compensation and Benefit Plans in force as of
          the date hereof, as required by law or under the terms of any
          collective bargaining agreement or any other action in the ordinary
          and usual course of business which would not significantly increase
          the cost of such plan to ARCO; and (C) actions necessary in order to
          extend the effectiveness of the Enhanced Retirement Program as set
          forth in Section 41 of the ARCO Retirement Plan, Section 19 of the
          CH-Twenty, Inc. Retirement Plan and Section 4A and 5A of the ARCO
          Special Termination Allowance Plan (the "Enhanced Retirement
          Program"), including but not limited to the final average salary
          feature, as currently in effect, for qualifying terminations of
          employment occurring within two years following the Effective Time;

                    (ii) increase the salary, wage, bonus or other compensation
          of any directors, officers or employees except for (A) increases
          occurring in the ordinary and usual course of business (which shall
          include normal periodic performance reviews and related compensation
          and benefit increases and increases reasonably required to maintain
          competitive compensation (based on market data) for specialized
          employees) and (B) the provision of individual compensation and
          benefit plans or agreements for newly hired or appointed officers or
          employees in the ordinary and usual course of business consistent with
          past practice; or

                    (iii) make any determination with respect to the
          satisfaction of performance objectives under the ARCO Compensation and
          Benefit Plans other than reasonable determinations that are consistent
          with past practice;

               3.1.2.5. subject to the provisions of Section 3.5.1, neither
          ARCO nor any of its Subsidiaries shall take any action or omit to take
          any action for the purpose of preventing, delaying or impeding the
          consummation of


                                      -31-

<PAGE>



          the Merger or the other transactions contemplated by this Agreement
          and the Stock Option Agreement including any action or omission that
          would cause (i) the Merger to fail to qualify as a reorganization
          under Section 368(a) of the Code or (ii) the exchange of BP Amoco
          Shares for ARCO Common Shares in the Merger to fail to qualify for
          nonrecognition of gain (except with respect to (a) cash received in
          lieu of fractional BP Amoco Shares or (b) stockholders of ARCO who are
          not Eligible ARCO Shareholders);

               3.1.2.6. ARCO shall timely satisfy, or cause to be timely
          satisfied, all applicable tax reporting and filing requirements
          contained in the Code with respect to the transactions contemplated
          hereby, including, without limitation, the reporting requirements
          contained in United States Treasury Regulation Section
          1.367(a)-3(c)(6);

               3.1.2.7. neither ARCO nor any of its Subsidiaries shall:

                    (i) without reasonable advance notice to and consultation
          with BP Amoco (unless BP Amoco is an adverse party with respect to
          such claim or litigation or to the extent such consultation would
          result in ARCO waiving its attorney-client privilege with respect to
          such claim or litigation), settle or compromise any claims or
          litigation where the amount of any such settlement or compromise
          exceeds $50,000,000; or

                    (ii) make any election with respect to taxes that could
          reasonably be expected to have a Material Adverse Effect on it;

               3.1.2.8. ARCO shall not modify any accounting policy except as
          may be required by changes in Law or in U.S. GAAP;

               3.1.2.9. ARCO shall not create, write down or change any material
          reserve, except in the ordinary and usual course of business, without
          reasonable advance notice to and consultation with BP Amoco; and

               3.1.2.10. neither ARCO nor any of its Subsidiaries shall
          authorize or enter into an agreement to do any of the foregoing.

         3.1.3. Consultation as to Material Contracts. ARCO shall cooperate
     with BP Amoco promptly after the date hereof in identifying and creating a
     list of Contracts that may be considered material to ARCO and its
     Subsidiaries. ARCO agrees that it will provide reasonable advance notice to
     and consult with BP Amoco with respect to any material amendment,
     modification or termination of, or


                                 -32-

<PAGE>



     any waiver, release or assignment of any material rights or claims under,
     the Contracts so identified and listed other than in the ordinary and usual
     course of business of ARCO and its Subsidiaries.

         3.2. ARCO Acquisition Proposals.

         3.2.1.  ARCO agrees that, subject to Section 3.2.3 and except as
     expressly contemplated by this Agreement, neither it nor any of its
     Subsidiaries nor any of the officers or directors of it or any of its
     Subsidiaries shall, and that it shall direct and use its best efforts to
     cause its and its Subsidiaries' employees, investment bankers, attorneys,
     accountants, financial advisors, agents or other representatives
     (collectively, the "ARCO Representatives") not to, directly or indirectly,
     initiate, solicit, encourage or otherwise facilitate any inquiries or the
     making of any proposal or offer with respect to a merger, reorganization,
     share exchange, dual-holding company transaction, consolidation or similar
     transaction involving ARCO, or any purchase of, or offer to purchase, all
     or substantially all of the equity securities of ARCO or of its and its
     Subsidiaries' assets taken as a whole (any such proposal or offer being
     hereinafter referred to as an "ARCO Acquisition Proposal"). ARCO further
     agrees that neither it nor any of its Subsidiaries nor any of its or its
     Subsidiaries' officers or directors shall, and that it shall direct and use
     its best efforts to cause the ARCO Representatives not to, directly or
     indirectly, have any discussions with or provide any confidential
     information or data to any Person relating to an ARCO Acquisition Proposal
     or engage in any negotiations concerning an ARCO Acquisition Proposal, or
     otherwise facilitate any effort or attempt to make or implement an ARCO
     Acquisition Proposal; provided, however, that nothing contained in this
     Agreement shall prevent ARCO or its board of directors from (i) making any
     disclosure to its stockholders if, in the good faith judgment of its board
     of directors, failure so to disclose would be inconsistent with its
     obligations under applicable Law; (ii) negotiating with or furnishing
     information to any Person who has made a bona fide written ARCO Acquisition
     Proposal which did not result from a breach of this Section 3.2.1; or (iii)
     recommending such an ARCO Acquisition Proposal to its stockholders (and in
     connection therewith withdraw its approval or favorable recommendation to
     stockholders of this Agreement), if and only to the extent that, in the
     case of actions referred to in clause (ii) or clause (iii), such ARCO
     Acquisition Proposal is a Superior Proposal (as defined below). For
     purposes of this Agreement, a "Superior Proposal" means any ARCO
     Acquisition Proposal by a third party (x) on terms which the board of
     directors of ARCO determines in its good faith judgment after consultation
     with its financial advisors, to be more favorable from a financial point of
     view to its stockholders than the Merger and the other transactions
     contemplated hereby, and (y) which the ARCO board of directors determines
     in its good faith judgment to constitute a transaction that is reasonably
     likely to be consummated on the terms


                                      -33-

<PAGE>



     set forth, taking into account all legal, financial, regulatory and other
     aspects of such proposal. ARCO agrees that it will, on the date hereof,
     immediately cease and cause to be terminated any existing activities,
     discussions or negotiations with any Person conducted heretofore with
     respect to any ARCO Acquisition Proposal. ARCO also agrees that if it has
     not already done so, it will promptly request each Person, if any, that has
     heretofore executed a confidentiality agreement within the 12 months prior
     to the date hereof in connection with its consideration of any ARCO
     Acquisition Proposal to return or destroy all confidential information
     heretofore furnished to such Person by or on behalf of it or any of its
     Subsidiaries.

         3.2.2.  ARCO agrees that it will take the necessary steps promptly to
     inform its Subsidiaries and its Subsidiaries' officers, directors and the
     ARCO Representatives of the obligations undertaken in this Section 3.2.
     ARCO agrees that it will notify BP Amoco promptly if any such inquiries,
     proposals or offers relating to or constituting an ARCO Acquisition
     Proposal are received by, any such information is requested from, or any
     such discussions or negotiations are sought to be initiated or continued
     with, any of its or its Subsidiaries' officers, directors and the ARCO
     Representatives indicating, in connection with such notice, the name of
     such Person and the material terms and conditions of any proposals or
     offers and thereafter shall keep BP Amoco informed, on a current basis, of
     the status and material terms and conditions of any such proposals or
     offers. ARCO shall give BP Amoco at least five business days' notice of all
     material terms and conditions of each ARCO Acquisition Proposal and the
     opportunity to respond to such ARCO Acquisition Proposal prior to any
     action by the ARCO board of directors approving the execution and delivery
     of a definitive agreement to implement a transaction in respect of such
     ARCO Acquisition Proposal.

         3.2.3.  Nothing contained herein shall prohibit ARCO from taking and
     disclosing to its stockholders a position contemplated by Rule 14e-2(a)
     under the Exchange Act with respect to an ARCO Acquisition Proposal by
     means of a tender or exchange offer.

         3.3.   Information Supplied.

         3.3.1. Registration Statement.

                3.3.1.1. Each of BP Amoco and ARCO shall cooperate with respect
         to and as promptly as practicable prepare, and BP Amoco shall file with
         the SEC as soon as practicable, a Registration Statement on Form F-4
         (the "Form F-4") under the Securities Act, with respect to the issuance
         pursuant to this Agreement of the BP Amoco Shares, which Registration


                                      -34-

<PAGE>


         Statement shall include the proxy statement/prospectus to be sent to
         holders of ARCO Common Shares (the "ARCO Proxy Statement") and, so far
         as appropriate, the BP Amoco Documents (as defined in Section 3.3.2.1).
         The Parties will cause the Form F-4 to comply as to form in all
         material respects with the applicable provisions of the Securities Act
         and the rules and regulations thereunder. Each of BP Amoco and ARCO
         shall use its respective best reasonable efforts to have the Form F-4
         declared effective by the SEC as promptly as practicable after such
         filing. BP Amoco shall use its reasonable efforts to obtain, prior to
         the effective date of the Form F-4, all necessary state securities law
         or "Blue Sky" permits or approvals required to carry out the
         transactions contemplated by this Agreement. BP Amoco will advise ARCO,
         promptly after it receives notice thereof, of the time when the Form
         F-4 has become effective or any supplement or amendment has been filed,
         the issuance of any stop order, the suspension of the qualification of
         the BP Amoco Shares issuable in connection with the Merger for offering
         or sale in any jurisdiction, or any request by the SEC for amendment of
         the ARCO Proxy Statement or the Form F-4 or comments thereon and
         responses thereto or requests by the SEC for additional information.

               3.3.1.2. BP Amoco and ARCO each agrees, as to itself and its
         Subsidiaries, that none of the information supplied or to be supplied
         by it or its Subsidiaries for inclusion or incorporation by reference
         in the Form F-4, including, without limitation, the ARCO Proxy
         Statement, and any amendment or supplement thereto will, at the time
         the Form F-4 becomes effective under the Securities Act, at the date of
         mailing to stockholders and at the time or times of the ARCO
         Stockholders Meeting (as defined in Section 3.4), contain any untrue
         statement of a material fact or omit to state any material fact
         required to be stated therein or necessary in order to make the
         statements therein, in the light of the circumstances under which they
         were made, not misleading. If at any time prior to the date of the ARCO
         Stockholders Meeting any information relating to ARCO or BP Amoco, or
         any of their respective Affiliates, officers or directors, should be
         discovered by ARCO or BP Amoco which should be set forth in an
         amendment to the Form F-4 or a supplement to the ARCO Proxy Statement,
         so that such document would not include any misstatement of a material
         fact or omit to state any material fact required to be stated therein
         or necessary to make the statements therein, in the light of the
         circumstances under which they were made, not misleading, the Party
         which discovers such information shall promptly notify the other Party
         and, to the extent required by Law, an appropriate amendment or
         supplement

                                      -35-

<PAGE>



         describing such information shall be promptly filed with the SEC and,
         to the extent required by law, disseminated to the ARCO stockholders.

               3.3.1.3. ARCO will use its best reasonable efforts to cause the
         definitive ARCO Proxy Statement to be mailed to its stockholders as
         promptly as practicable after the date hereof.

         3.3.2.BP Amoco Documents.

               3.3.2.1. BP Amoco shall, with the reasonable assistance of ARCO,
         as promptly as practicable prepare and file with the LSE (a) a circular
         to be sent to BP Amoco shareholders in connection with the BP Amoco
         Shareholders Meeting (as defined in Section 3.4) (the "BP Amoco
         Circular"), containing (i) a notice convening the BP Amoco Shareholders
         Meeting, (ii) such other information (if any) as may be required by the
         LSE and (iii) such other information as BP Amoco and ARCO shall agree
         to include therein; and (b) listing particulars or an exempt listing
         document relating to BP Amoco and its Subsidiaries and the BP Amoco
         Ordinary Shares (together with any summary thereof, the "BP Amoco
         Listing Document," and the BP Amoco Circular and the BP Amoco Listing
         Document, together, the "BP Amoco Documents"). BP Amoco and ARCO each
         agrees, as to itself and its Subsidiaries, that the BP Amoco Documents
         and any supplements thereto and any circulars or documents issued to
         shareholders, employees or debentureholders of BP Amoco, will contain
         all particulars relating to BP Amoco and ARCO required to comply in all
         material respects with all United Kingdom statutory and other legal
         provisions (including, without limitation, the Companies Act, the
         Financial Services Act 1986 (the "FSA") and the rules and regulations
         made thereunder, and the rules and requirements of the LSE) and all
         such information contained in the BP Amoco Documents will be
         substantially in accordance with the facts and will not omit anything
         material likely to affect the import of such information.

               3.3.2.2. BP Amoco will use its best reasonable efforts to cause
         the BP Amoco Documents to receive any clearance thereof required from
         the LSE and to cause the definitive BP Amoco Documents to be mailed to
         its shareholders, in each case as promptly as practicable after the
         date hereof.

               3.3.2.3. Notwithstanding any of the other provisions of this
         Section 3.3 and for the avoidance of doubt, BP Amoco hereby agrees that
         (i) for the purposes of the preparation of the BP Amoco Circular and
         the BP Amoco Listing Document and any amendments or supplements
         thereto, 


                                 -36-

<PAGE>


         ARCO shall only be obliged (pursuant to such other provisions) to
         supply BP Amoco with information to the extent that it relates solely
         to ARCO and/or its Subsidiaries, and (ii) neither ARCO, nor any of its
         Subsidiaries, nor any of its or their directors or other officers shall
         accept any responsibility for either the BP Amoco Circular or the BP
         Amoco Listing Document or the information included therein or omitted
         therefrom.

         3.4. Shareholders Meetings. ARCO will take all action necessary to
convene a special meeting of the holders of ARCO Common Shares at which the
holders of ARCO Common Shares shall consider the adoption of this Agreement
(including any adjournments or postponements thereof, the "ARCO Stockholders
Meeting") as promptly as practicable after the Form F-4 has been declared
effective by the SEC. BP Amoco will take all action necessary to convene an
extraordinary general meeting of BP Amoco shareholders at which an ordinary
resolution will be proposed to consider the approval of the Merger (the "BP
Amoco Shareholder Meeting") after the BP Amoco Documents are cleared by the LSE
and the Form F-4 has been declared effective by the SEC. BP Amoco and ARCO each
agrees to use best reasonable efforts such that, to the extent practical, the
ARCO Stockholders Meeting and the BP Amoco Shareholders Meeting each shall be
held as promptly as practicable after the conditions precedent to holding such
meeting have been fulfilled and as nearly contemporaneously as practicable.
Subject to the terms of this Agreement, including the provisions of Section 3.2,
the board of directors of each of BP Amoco and ARCO shall recommend to its
respective shareholders, in the case of BP Amoco, the approval of the Merger
and, in the case of ARCO, the adoption of the Merger Agreement and shall use
best reasonable efforts to solicit such adoption unless it concludes, in the
exercise of its fiduciary duties, after consultation with outside counsel, that
the Merger is no longer advisable for its shareholders; provided, however, that
neither BP Amoco nor ARCO shall be entitled to withdraw its recommendation to
its respective shareholders if to do so would be inconsistent with the
obligations it has expressly assumed elsewhere in this Agreement. In the event
that subsequent to the date hereof, the board of directors of BP Amoco and/or
ARCO determines that the Merger or the Merger Agreement, as the case may be, is
no longer advisable and recommends that its respective shareholders reject it,
BP Amoco shall nevertheless submit the Merger to the holders of BP Amoco Voting
Shares for approval at the BP Amoco Shareholders meeting and ARCO shall
nevertheless submit this Agreement to the holders of ARCO Common Shares, for
adoption at the ARCO Stockholders Meeting, in each case unless this Agreement
shall have been terminated in accordance with its terms prior to the date of the
applicable meeting.


                                      -37-

<PAGE>



         3.5.   Filings; Other Actions; Notification.

         3.5.1. BP Amoco and ARCO shall each cooperate with the other and (i)
     use (and shall use best reasonable efforts to cause their respective
     Subsidiaries to use) all their respective best reasonable efforts promptly
     to take or cause to be taken all actions, and do or cause to be done all
     things, necessary, proper or advisable under this Agreement, the Stock
     Option Agreement and applicable Laws to consummate and make effective the
     Merger and the other transactions contemplated by this Agreement and the
     Stock Option Agreement as soon as practicable, including preparing and
     filing as promptly as practicable all documentation to effect all necessary
     filings, notices, petitions, statements, registrations, submissions of
     information, applications and other documents, (ii) use (and shall use best
     reasonable efforts to cause their respective Subsidiaries to use) all their
     respective best reasonable efforts to obtain as promptly as practicable all
     approvals, consents, registrations, permits, authorizations and other
     confirmations required to be obtained from any third party (other than BP
     Amoco Required Consents and ARCO Required Consents) necessary, proper or
     advisable to consummate the Merger and the other transactions contemplated
     by this Agreement and the Stock Option Agreement, and (iii) use (and shall
     use best reasonable efforts to cause their respective Subsidiaries to use)
     their respective best reasonable efforts to take or cause to be taken all
     actions, and do or cause to be done all things, necessary, proper or
     advisable to obtain the BP Amoco Required Consents or ARCO Required
     Consents, as the case may be; it being understood that, for purposes of
     this Section 3.5, the Parties agree that "best reasonable efforts" shall
     require (without limitation of any other meaning of such words) each Party
     to accept or agree to, at such time as may be required to cause the
     condition set forth in Section 4.1.2 to be fulfilled prior to the
     Termination Date, as it may be extended pursuant to Section 5.2, any
     conditions, terms or restrictions in connection with any such BP Amoco
     Required Consent or ARCO Required Consent, as the case may be, unless all
     such conditions, terms and restrictions, in the aggregate, would be
     reasonably likely to have a Material Adverse Effect on BP Amoco or ARCO
     after the Effective Time (it being understood that, for this purpose
     materiality shall be considered solely with respect to the total value of
     the U.S. operations of BP Amoco, ARCO and their Subsidiaries, taken
     together). Subject to applicable Laws relating to the exchange of
     information, BP Amoco and ARCO shall have the right to review in advance,
     and to the extent practicable each will consult the other on, all the
     information relating to ARCO and its Subsidiaries or BP Amoco and its
     Subsidiaries, as the case may be, that appears in any filing made with, or
     written materials submitted to, any third party and/or any Governmental
     Entity in connection with the Merger and the other transactions
     contemplated by this Agreement and the Stock Option

                                 -38-

<PAGE>



     Agreement. In exercising the foregoing right, each of BP Amoco and ARCO
     shall act reasonably and as promptly as practicable.

         3.5.2.  BP Amoco and ARCO each shall, upon request by and reasonable
     notice from the other, furnish the other with all information concerning
     itself, its Subsidiaries, directors, officers and shareholders or
     stockholders and such other matters as may be reasonably necessary or
     advisable in connection with the Form F-4, the BP Amoco Documents, the ARCO
     Proxy Statement or any other necessary or appropriate filing, notice,
     petition, statement, registration, submission of information or application
     made by or on behalf of BP Amoco or ARCO or any of their respective
     Subsidiaries to any third party and/or any Governmental Entity in
     connection with the Merger and the other transactions contemplated by this
     Agreement and the Stock Option Agreement.

         3.5.3.  BP Amoco and ARCO each shall keep the other apprised of the
     status of matters relating to completion of the Merger and the other
     transactions contemplated by this Agreement and the Stock Option Agreement,
     including promptly furnishing the other with copies of notices or other
     communications received by BP Amoco or ARCO, as the case may be, or any of
     its Subsidiaries, from any third party and/or any Governmental Entity with
     respect to the Merger and the other transactions contemplated by this
     Agreement and the Stock Option Agreement. BP Amoco and ARCO each shall give
     prompt notice to the other of any change that would, individually or in the
     aggregate, reasonably be expected to result in a Material Adverse Effect on
     it or of any failure of any condition set forth in Article IV to the other
     Party's obligations to effect the Merger.

         3.5.4. Prior to making any filing, notice, petition, statement,
     registration, submission of information or application to or with any third
     party and/or Governmental Entity (including any domestic or foreign
     national securities exchange) in connection with the consummation of the
     Merger and the other transactions contemplated by this Agreement and the
     Stock Option Agreement and except as may be required by Law or by
     obligations pursuant to any listing agreement with or rules of any domestic
     or foreign national securities exchange, each Party shall make all
     reasonable efforts to consult with the other Party with respect to the
     content of such filing, notice, petition, statement, registration,
     submission of information or application and to provide the other Party
     with copies of the proposed filing, notice, petition, statement,
     registration, submission of information or application. Neither BP Amoco
     nor ARCO shall agree to participate in any meeting with any Governmental
     Entity in respect of any filings, investigation or other inquiry relating
     to the Merger and the other transactions contemplated by this Agreement or
     the Stock Option Agreement unless it consults with the other Party in
     advance and, to the extent practicable and permitted by

                                      -39-

<PAGE>



     such Governmental Entity, gives the other Party the opportunity to attend
     and participate thereat.

         3.5.5. In the event any claim, action, suit, investigation or other
     proceeding by any Governmental Entity or other Person or other legal or
     administrative proceeding is commenced that questions the validity or
     legality of this Agreement, the Stock Option Agreement, or the Merger or
     the other transactions contemplated by this Agreement and the Stock Option
     Agreement or claims damages in connection therewith, the Parties agree to
     cooperate and use their best reasonable efforts, subject to the limitations
     set forth in Section 3.5.1, to defend against, respond to and resolve such
     claim, action, suit, investigation or other proceeding in a manner that
     permits the consummation of the Merger prior to the Termination Date.

         3.6. Access. In order to facilitate consummation of the Merger and the
other transactions contemplated by this Agreement, the Parties hereby agree that
upon reasonable request to any executive officer of BP Amoco or ARCO, as the
case may be, designated for the purpose, and except as may otherwise be required
by applicable Law, BP Amoco and ARCO each shall (and shall cause its
Subsidiaries to) afford the other's officers, employees, investment bankers,
attorneys, accountants, financial advisors, agents or other representatives
reasonable access, during normal business hours throughout the period prior to
the Effective Time, to its properties, books, contracts and records and, during
such period, each shall (and shall cause its Subsidiaries to) furnish promptly
to the other all information concerning its business, properties and personnel
as may reasonably be requested, provided that no receipt of information pursuant
to this Section shall affect or be deemed to modify any representation or
warranty made by BP Amoco or ARCO hereunder, and provided, further, that the
foregoing shall not require BP Amoco or ARCO to permit any inquiry, or to
disclose any information, that in the reasonable judgment of BP Amoco or ARCO,
as the case may be, would (i) violate any antitrust or competition Law or (ii)
result in the disclosure of any trade secrets of third parties or violate any of
its obligations with respect to confidentiality to third parties unless the
consent of such third party is obtained (and BP Amoco or ARCO, as the case may
be, shall use its reasonable efforts to obtain the consent of such third party
to such inspection or disclosure). All such information shall be governed by the
terms of the Confidentiality Agreement, dated January 28, 1999, between BP Amoco
and ARCO (the "Confidentiality Agreement"), including without limitation all
such information disclosed in the Disclosure Letters.

         3.7. Publicity. The initial press release concerning this Agreement,
the Merger and the other transactions contemplated by this Agreement and the
Stock Option Agreement shall be a joint press release, and thereafter BP Amoco
and ARCO shall consult with each other prior to issuing any press releases or
otherwise making public 
                                      -40-

<PAGE>



announcements with respect to the Merger and the other transactions contemplated
by this Agreement and the Stock Option Agreement.

         3.8. Benefits and Other Matters.

               3.8.1. Employee Benefits.

               3.8.1.1. It is the specific intention of the Parties that the
         compensation and benefit programs (including annual and long-term
         incentive programs) to be provided by BP Amoco and its Subsidiaries for
         current and former employees of ARCO will be no less favorable in the
         aggregate than is provided to similarly situated employees of BP Amoco
         and its Subsidiaries.

               3.8.1.2. For at least one year following the Effective Time, BP
         Amoco shall provide or cause to be provided to current and former
         employees and directors of ARCO and its Subsidiaries compensation and
         benefits that are at least as favorable in the aggregate (taking into
         account the benefits provided pursuant to this Section 3.8) as the
         compensation and benefits they were entitled to receive immediately
         prior to the Effective Time (including, without limitation, benefits
         pursuant to qualified and non-qualified retirement plans, savings
         plans, medical plans and programs, deferred compensation arrangements,
         incentive plans, and retiree benefit plans, policies and arrangements);
         provided, however, that, with respect to employees who are subject to
         collective bargaining, all benefits shall be provided in accordance
         with the applicable collective bargaining or other labor agreements;
         and provided, further, that all incentive, bonus and similar plans
         shall after the Effective Time be substantially performance-based.

               3.8.1.3. BP Amoco shall cause (i) ARCO's and its Subsidiaries'
         (other than Vastar's) existing severance programs (as in effect
         immediately prior to the Effective Time) to continue without any
         reduction in benefits for at least two years following the Effective
         Time; (ii) beginning with the first full plan year after the Effective
         Time, interest to be credited to the accounts of participants under the
         Acorn Executive Deferral Plan (as in effect at the Effective Time) at
         the greater of (x) the interest rate credited under a comparable Oak
         plan maintained in the United States for senior executives or (y) the
         "Citibank Base Rate," as defined in the Acorn Executive Deferral Plan;
         provided, however, that for the period ending upon completion of ten
         full plan years after the Effective Time, such rate shall be no less
         than 125% of the 120-month rolling average of the 10-year

                                      -41-

<PAGE>



         U.S. Treasury Note rate for each applicable 120-month period ending
         June 30 (determined in a manner consistent with past practice), such
         rate to be effective for the immediately following plan year, except
         that the minimum rate shall be the Citibank Base Rate in those limited
         circumstances in which it is determined by Acorn management, in its
         sole discretion pursuant to a formal action taken prior to the
         Effective Time, that any participant has failed to satisfactorily
         perform his/her duties consistent with pre-established goals previously
         communicated to the participant and such failure to so perform has not
         otherwise been excused by Acorn management; and (iii) the ARCO
         outplacement policies and, for executives, financial counseling
         policies, as in effect as of the date hereof, to be maintained for two
         years following the Effective Time.

               3.8.1.4. Following the Effective Time, BP Amoco shall, and shall
         cause its Subsidiaries to, recognize service with ARCO and its
         Subsidiaries and any predecessor entities (and any other service
         credited by ARCO under similar benefit plans), prior to the Effective
         Time for all purposes (including, without limitation, eligibility to
         participate, vesting, benefit accrual, eligibility to commence benefits
         and severance) under any benefit plans of BP Amoco or its Subsidiaries
         in which the particular employee or former employee of ARCO (or its
         respective Subsidiaries) participates to the same extent as if such
         service had been rendered to BP Amoco or any of its Subsidiaries;
         provided however, that the foregoing shall not result in any
         duplication of benefits for the same period of service. From and after
         the Effective Time, BP Amoco shall, and shall cause its Subsidiaries
         to, recognize any and all appropriate out-of-pocket expenses of each
         employee or former employee of ARCO and its Subsidiaries for purposes
         of determining such employee's and former employee's (including their
         beneficiaries and dependents) deductible and co-payment expenses under
         BP Amoco's medical benefit plans. BP Amoco shall waive, or cause to be
         waived, any pre-existing condition limitation under any welfare benefit
         plan maintained by BP Amoco or any of its Subsidiaries in which
         employees of ARCO and its Subsidiaries (and their respective eligible
         dependents) will be eligible to participate on or following the
         Effective Time to the extent such pre-existing condition limitation was
         waived or satisfied under the comparable ARCO plan.

               3.8.1.5. From and after the Effective Time, BP Amoco shall honor,
         fulfill and discharge, and shall cause its Subsidiaries to honor,
         fulfill and discharge, in accordance with its terms, each existing
         employment, change of control, severance and termination agreement
         between ARCO or any of its Subsidiaries, and any officer, director or
         employee of such company, 


                                 -42-

<PAGE>



         including without limitation (i) all legal and contractual obligations
         pursuant to outstanding retirement plans, including the extension of
         the Enhanced Retirement Program, pursuant to Section 3.1.2.4(i), salary
         and bonus deferral plans, vested and accrued benefits and similar
         employment and benefit arrangements and agreements in effect as of the
         Effective Time, including all the "change of control" provisions under
         the plans, programs, policies and agreements listed in Section 3.8.1.5
         of the ARCO Disclosure Letter, and (ii) all vacation, personal and sick
         days accrued by employees of ARCO and its Subsidiaries as of the
         Effective Time. BP Amoco acknowledges that the consummation of the
         Merger will constitute a "change of control" as respectively defined
         under the plans, programs, policies and agreements listed in Section
         3.8.1.5 of the ARCO Disclosure Letter.

               3.8.1.6. From and after the Effective Time, BP Amoco shall
         recognize, and cooperate in good faith with, the Independent Plan
         Administrator (the "IPA") of the ARCO Supplemental Executive Benefit
         Plans Trust Agreement; provided, however, that BP Amoco agrees to
         cooperate with ARCO and the IPA in an effort to effect the transfer
         and/or assumptions of any plan, or portion thereof, under the
         administration of ARCO or the IPA to any successor plan or trust, as
         may be requested by ARCO or the IPA.

               3.8.2.Director and Officer Liability.

               3.8.2.1. BP Amoco agrees that all rights to indemnification and
         all limitations on liability existing in favor of any Indemnitee (as
         defined below) in respect of acts or omissions of such Indemnitees on
         or prior to the Effective Time as provided in the restated certificate
         of incorporation and by-laws of ARCO or an agreement between an
         Indemnitee and ARCO or its Subsidiaries in effect as of the date hereof
         shall continue in full force and effect in accordance with the terms
         thereof.

               3.8.2.2. For six years after the Effective Time, BP Amoco shall
         indemnify and hold harmless the individuals who on or prior to the
         Effective Time were officers or directors of ARCO or any of its
         Subsidiaries (the "Indemnitees") (i) with respect to all acts or
         omissions by them in their capacities as officers or directors of ARCO
         in connection with the approval of this Agreement and the transactions
         contemplated hereby and (ii) to the same extent indemnified as set
         forth in Section 3.8.2.1, with respect to all other actions or
         omissions by them in their capacities as officers or directors of ARCO,
         or taken by them at the request of, ARCO

                                 -43-

<PAGE>



         or any of its Subsidiaries. In the event any claim in respect of which
         indemnification is available pursuant to the foregoing provisions is
         asserted or made within such six-year period, all rights to
         indemnification shall continue until such claim is disposed of or all
         judgments, orders, decrees or other rulings in connection with such
         claim are duly satisfied.

              3.8.2.3. For six years after the Effective Time, BP Amoco shall
         procure the provision of directors' and officers' liability insurance
         in respect of acts or omissions occurring prior to the Effective Time
         covering each such Person currently covered by ARCO's directors' and
         officers' liability insurance policy on terms set forth in the BP Amoco
         Disclosure Letter. Such liability insurance procured by BP Amoco may
         provide "first dollar" coverage, without any requirement to first seek
         indemnification from the Surviving Corporation or BP Amoco.

              3.8.2.4. The obligations of BP Amoco under this Section 3.8.2
         shall not be terminated or modified in such a manner as to adversely
         affect any Indemnitee to whom this Section 3.8.2 applies without the
         consent of such affected Indemnitee (it being expressly agreed that the
         Indemnitees to whom this Section 3.8.2 applies shall be third party
         beneficiaries of this Section 3.8.2).

         3.9. Expenses. Except as otherwise provided in Section 5.5, whether or
not the Merger is consummated, all costs and expenses incurred in connection
with this Agreement, the Stock Option Agreement, the Merger and the other
transactions contemplated by this Agreement and the Stock Option Agreement shall
be paid by the party incurring such expense, except that the parties shall share
equally the costs and expenses of filing, printing and distributing the Form
F-4, the ARCO Proxy Statement, the BP Amoco Documents and related documents.

         3.10. Takeover Statutes. If any Takeover Statute is or may become
applicable to the Merger or the other transactions contemplated by this
Agreement and the Stock Option Agreement, each of BP Amoco and ARCO and its
board of directors shall, subject to applicable Law, grant such approvals and
take such actions as are necessary so that the Merger and the other transactions
contemplated by this Agreement and the Stock Option Agreement may be consummated
as promptly as practicable on the terms contemplated by this Agreement and the
Stock Option Agreement, and otherwise act to eliminate or minimize the effects
of such Takeover Statute on such transactions.

         3.11. Dividends. At least until December 31, 2003, dividends on the BP
Amoco Ordinary Shares will be announced in U.S. dollars and paid to holders of
BP Amoco Depositary Shares in U.S. dollars and to holders of BP Amoco Ordinary
Shares in 

                                 -44-

<PAGE>



pounds sterling. ARCO agrees that it will coordinate its record dates for
dividends on ARCO Common Shares with BP Amoco's record dates for dividends on BP
Amoco Ordinary Shares so that record dates with respect to dividends to which
holders of ARCO Common Shares will be entitled, whether declared with respect to
ARCO Common Shares or, after the Effective Time, with respect to BP Amoco
Ordinary Shares, do not occur more or less frequently than once each calendar
quarter.

         3.12. Listing Applications. BP Amoco shall promptly prepare and submit
to the LSE a listing application with respect to the BP Amoco Ordinary Shares
issuable in the Merger, and to each of the NYSE and Pacific Exchange a listing
application in respect of the BP Amoco Depositary Shares issuable in the Merger,
and shall use its best efforts to obtain, prior to the Effective Time, approval
for the listing of such BP Amoco Ordinary Shares, in the case of the LSE,
subject to allotment, and such BP Amoco Depositary Shares, in the case of the
NYSE, subject to official notice of issuance.

         3.13. Letters of Accountants.

         3.13.1. BP Amoco shall use its best reasonable efforts to cause to be
     delivered to ARCO "comfort" letters of Ernst & Young, BP Amoco's
     independent public accountants, dated the effective date of the Form F-4
     and the Closing Date, respectively, and addressed to ARCO and its
     directors, in form reasonably satisfactory to ARCO and customary in scope
     and substance for "comfort" letters delivered by independent public
     accountants in connection with registration statements similar to the Form
     F-4.

         3.13.2. ARCO shall use its best reasonable efforts to cause to be
     delivered to BP Amoco "comfort" letters of PricewaterhouseCoopers, ARCO's
     independent public accountants, dated the effective date of the Form F-4
     and the Closing Date, respectively, and addressed to BP Amoco and its
     directors, in form reasonably satisfactory to BP Amoco and customary in
     scope and substance for "comfort" letters delivered by independent public
     accountants in connection with registration statements similar to the Form
     F-4.

         3.14. Agreements of ARCO Affiliates. Prior to the date of the ARCO
Stockholders Meeting, ARCO shall cause to be prepared and delivered to BP Amoco
a list identifying all persons who, at the time of the ARCO Stockholders
Meeting, ARCO believes may be deemed to be "affiliates" of ARCO for purposes of
Rule 145 under the Securities Act (the "ARCO Affiliates"). BP Amoco shall be
entitled to place restrictive legends on any BP Amoco ADRs (or any underlying BP
Amoco Ordinary Shares that may be withdrawn upon surrender of such BP Amoco
ADRs) received by such ARCO Affiliates. ARCO shall use its best efforts to cause
each person who is identified as an ARCO Affiliate in such list to deliver to BP
Amoco, at or prior to the Effective Time, a 


                                      -45-

<PAGE>



written agreement, in the form to be approved by the Parties, that such ARCO
Affiliate will not sell, pledge, transfer or otherwise dispose of any BP Amoco
Depositary Shares or BP Amoco Ordinary Shares issued to such ARCO Affiliate
pursuant to the Merger (or any underlying BP Amoco Ordinary Shares that may be
withdrawn upon surrender of such BP Amoco Depositary Shares), except pursuant to
an effective registration statement or in compliance with Rule 145 or an
exemption from the registration requirements of the Securities Act. BP Amoco
shall not register the transfer of any BP Amoco Ordinary Shares and shall cause
the Depositary not to register the transfer of any BP Amoco Depositary Shares
unless such transfer is made in compliance with the foregoing.

         3.15. Accounting Matters. At least until December 31, 2003, BP Amoco
shall include as supplemental disclosure in its consolidated financial
statements a reconciliation of its consolidated net income and shareholders'
equity to U.S. GAAP.

         3.16. Tax Matters. BP Amoco shall timely satisfy, or cause to be timely
satisfied, all applicable tax reporting and filing requirements contained in the
Code with respect to the transactions contemplated hereby, including, without
limitation, the reporting requirements contained in the United States Treasury
Regulation Section 1.367(a)-3(c)(6).

         3.17. Vastar. Notwithstanding anything to the contrary in this Article
III, if any action is taken by Vastar or any of its Subsidiaries, or Vastar or
any of its Subsidiaries fails to take any action, that would (but for this
Section 3.17) constitute a violation by ARCO of a provision of this Article III,
ARCO shall be deemed to be in compliance with, and deemed not in violation of,
such provision if ARCO has used reasonable efforts, consistent with the
fiduciary duties of the Vastar directors designated by ARCO, to prevent such
action or such failure to take action, as the case may be, on the part of Vastar
and its Subsidiaries. For the purposes of Section 3.1.2.3, transactions by
Vastar and its Subsidiaries shall not count toward the monetary amounts set
forth therein.

         3.18. Section 103. BP Amoco shall, if and to the extent required,
comply with its obligations under Section 103 of the U.K. Companies Act 1985 in
respect of the Merger Consideration.


                                   ARTICLE IV

                                   Conditions

         4.1. Conditions to Each Party's Obligation to Effect the Merger. The
respective obligations of BP Amoco, Merger Sub and ARCO to effect the Merger are
subject to the satisfaction or waiver of each of the following conditions:


                                      -46-

<PAGE>



         4.1.1.  Shareholder Approvals. This Agreement shall have been duly
     adopted by holders of ARCO Common Shares constituting the ARCO Requisite
     Vote, and the Merger shall have been duly approved by the shareholders of
     BP Amoco constituting the BP Amoco Requisite Vote.

         4.1.2.  Regulatory Consents. All BP Amoco Required Consents and ARCO
     Required Consents from or with any Governmental Entity (collectively,
     "Governmental Consents") in connection with the consummation of the Merger
     and the other transactions contemplated hereby shall have been made or
     obtained, except where the failure to obtain such Governmental Consent
     would not, individually or in the aggregate, reasonably be expected to have
     a Material Adverse Effect on BP Amoco or ARCO after the Effective Time, and
     such Governmental Consents shall not contain any terms or impose any
     conditions, terms or restrictions in connection with any such Governmental
     Consent which, individually or in the aggregate, would be reasonably likely
     to have a Material Adverse Effect on BP Amoco or ARCO after the Effective
     Time (it being understood that, for this purpose, materiality shall be
     considered solely with respect to the total value of the U.S. operations of
     BP Amoco, ARCO and their Subsidiaries, taken together.

         4.1.3. Laws and Orders. No Governmental Entity of competent
     jurisdiction shall have enacted, issued, promulgated, enforced or entered
     any Law (whether temporary, preliminary or permanent) that is in effect and
     restrains, enjoins or otherwise prohibits the consummation of the Merger or
     the other transactions contemplated by this Agreement and that,
     individually or in the aggregate with all other such Laws, is reasonably
     likely to have a Material Adverse Effect on BP Amoco or ARCO or that would
     materially impair the ability of BP Amoco to consummate the Merger
     (collectively, an "Order"). The enactment, issuance, promulgation,
     enforcement or execution by any Governmental Entity of any Order with
     respect to a Governmental Consent shall not result in a failure of the
     conditions set forth in this Section 4.1.3 if such Order imposes on BP
     Amoco or ARCO or their respective Subsidiaries conditions, terms or
     restrictions with respect to or upon the consummation of the Merger and
     such conditions, terms or restrictions, if contained solely in a
     Governmental Consent, would not result in the failure of the condition set
     forth in Section 4.1.2.

         4.1.4. Effectiveness of Form F-4. The Form F-4 shall have become
     effective prior to the mailing of the ARCO Proxy Statement to its
     stockholders, no stop order suspending the effectiveness of the Form F-4
     shall then be in effect, and no proceedings for that purpose shall then be
     threatened by the SEC or shall have been initiated by the SEC and not
     concluded or withdrawn.


                                      -47-

<PAGE>


         4.1.5.  Exchange Listings. The LSE shall have granted permission for
     admission to the Official List of the LSE, subject to allotment, of the BP
     Amoco Ordinary Shares to be issued pursuant to the Merger, and such
     permission shall not have been withdrawn prior to the Effective Time, and
     the BP Amoco Depositary Shares shall have been authorized for listing on
     the NYSE, subject to official notice of issuance.

         4.2. Conditions to Obligations of BP Amoco and Merger Sub. The
obligations of BP Amoco and Merger Sub to effect the Merger is also subject to
the satisfaction or waiver by BP Amoco and Merger Sub prior to the Effective
Time of the following conditions:

         4.2.1. Representations and Warranties of ARCO. The representations and
     warranties of ARCO set forth in this Agreement (i) to the extent qualified
     by Material Adverse Effect or any other materiality qualification shall be
     true and correct and (ii) to the extent not qualified by Material Adverse
     Effect or any other materiality qualification shall be true and correct, in
     each case when made and as of the Closing Date as though made on and as of
     the Closing Date (except as provided in Section 2.2 and except that any
     representation or warranty that by its terms expressly speaks as of an
     earlier date shall be true and correct as of such date) (provided that this
     clause (ii) shall be deemed satisfied so long as any failures of such
     representations and warranties to be true and correct, taken together,
     would not, individually or in the aggregate, reasonably be expected to have
     a Material Adverse Effect on ARCO), and BP Amoco shall have received a
     certificate signed on behalf of ARCO by an executive officer of ARCO to
     such effect.

         4.2.2.  Performance of Obligations of ARCO. ARCO shall have performed
     all material obligations required to be performed by it under this
     Agreement at or prior to the Closing Date, and BP Amoco shall have received
     a certificate signed on behalf of ARCO by an executive officer of ARCO to
     such effect.

         4.3. Conditions to Obligation of ARCO. The obligation of ARCO to effect
the Merger is also subject to the satisfaction or waiver by ARCO prior to the
Effective Time of the following conditions:

         4.3.1. Representations and Warranties. The representations and
     warranties of BP Amoco and Merger Sub set forth in this Agreement (i) to
     the extent qualified by Material Adverse Effect or any other materiality
     qualification shall be true and correct and (ii) to the extent not
     qualified by Material Adverse Effect or any other materiality qualification
     shall be true and correct, in each case when


                                      -48-

<PAGE>


     made and as of the Closing Date as though made on and as of the Closing
     Date (except that any representation or warranty that by its terms
     expressly speaks as of an earlier date shall be true and correct as of such
     date) (provided that this clause (ii) shall be deemed satisfied so long as
     any failures of such representations and warranties to be true and correct,
     taken together, would not, individually or in the aggregate, reasonably be
     expected to have a Material Adverse Effect on BP Amoco), and ARCO shall
     have received a certificate signed on behalf of BP Amoco by an executive
     officer of BP Amoco to such effect.

         4.3.2.  Performance of Obligations of BP Amoco. BP Amoco shall have
     performed all material obligations required to be performed by it under
     this Agreement at or prior to the Closing Date, and ARCO shall have
     received a certificate signed on behalf of BP Amoco by an executive officer
     of BP Amoco to such effect.

         4.3.3.  Tax Opinion. ARCO shall have received an opinion from Cravath,
     Swaine & Moore, dated as of the Effective Time, substantially to the effect
     that, on the basis of the facts, representations and assumptions set forth
     in such opinion, the Merger will be treated for U.S. federal income tax
     purposes as a reorganization within the meaning of Section 368(a) of the
     Code and that no gain or loss will be recognized by the stockholders of
     ARCO who exchange ARCO Common Shares solely for BP Amoco Shares pursuant to
     the Merger (except with respect to (i) cash received in lieu of fractional
     BP Amoco Shares or (ii) stockholders of ARCO who are not Eligible ARCO
     Shareholders). In rendering such opinion, counsel may require and rely upon
     representation letters of BP Amoco and ARCO substantially in the form set
     forth as Exhibits B and C hereto, respectively.


                                    ARTICLE V

                                   Termination

         5.1. Termination by Mutual Consent. This Agreement may be terminated
and the Merger may be abandoned at any time prior to the Effective Time, whether
before or after the approval by shareholders of BP Amoco and the stockholders of
ARCO referred to in Section 4.1.1, by mutual written consent of BP Amoco and
ARCO, by action of their respective boards of directors.

         5.2. Termination by Either BP Amoco or ARCO. This Agreement may be
terminated and the Merger may be abandoned at any time prior to the Effective
Time by action of the board of directors of either BP Amoco or ARCO if (i) the
Merger shall not have been consummated by March 31, 2000, whether such date is
before or after the


                                      -49-

<PAGE>



approvals by the shareholders of BP Amoco and the stockholders of ARCO (subject
to extension as provided below, the "Termination Date"), (ii) any Order
permanently restraining, enjoining or otherwise prohibiting the consummation of
the Merger shall have become final and non-appealable, whether before or after
the approval by the shareholders of BP Amoco or the stockholders of ARCO, (iii)
this Agreement shall not have been adopted by holders of ARCO Common Shares
constituting the ARCO Requisite Vote at the duly held ARCO Stockholders Meeting,
including any adjournment or postponement thereof or (iv) the Merger shall not
have been approved by shareholders of BP Amoco constituting the BP Amoco
Requisite Vote at the duly held BP Amoco Shareholders Meeting, including any
adjournment or postponement thereof; provided that the right to terminate this
Agreement pursuant to this Section 5.2 shall not be available to a Party that
has breached in any material respect its obligations under Section 3.5 or any of
its other obligations under this Agreement in any manner that shall have
proximately contributed to the failure of the Merger to be consummated;
provided, further, that, if a condition set forth in Section 4.1.2 or 4.1.3
remains unsatisfied and shall not have been waived by each of the parties hereto
on or prior to the Termination Date, either ARCO or BP Amoco may extend the
Termination Date to June 30, 2000. The party electing pursuant to the foregoing
proviso to extend the Termination Date shall deliver written notice to such
effect to the other party on or before March 31, 2000, whereupon such extension
shall be effective from and after April 1, 2000, and this Agreement may not be
terminated and the Merger abandoned pursuant to Section 5.2(i) until after such
extended Termination Date.

         5.3. Termination by BP Amoco. This Agreement may be terminated and the
Merger may be abandoned at any time prior to the Effective Time, whether before
or after the approval by the shareholders of BP Amoco referred to in Section
4.1.1, by action of the board of directors of BP Amoco, if (i) the board of
directors of ARCO shall have withdrawn its approval or favorable recommendation
to stockholders of this Agreement; or (ii) ARCO or its board of directors shall
take any of the actions described in clause (ii) or clause (iii) of the proviso
to Section 3.2.1; or (iii) there shall be a breach by ARCO of any
representation, warranty, covenant or agreement contained in this Agreement
which would result in a failure of a condition set forth in Section 4.2.1 or
4.2.2 and cannot be or is not cured prior to the Termination Date.

         5.4. Termination by ARCO. This Agreement may be terminated and the
Merger may be abandoned at any time prior to the Effective Time, whether before
or after the approval by stockholders of ARCO referred to in Section 4.1.1, by
action of the board of directors of ARCO, if (i) the board of directors of BP
Amoco shall have withdrawn its approval or favorable recommendation to
shareholders of the Merger or (ii) the board of directors of ARCO becomes
entitled pursuant to Section 3.2.1 to recommend an ARCO Acquisition Proposal to
its stockholders and, (A) at the time of such termination pursuant to this
clause (ii), ARCO is in compliance with Section 3.2.1, (B) ARCO first pays to BP
Amoco the ARCO Termination Amount and any amounts due to BP Amoco under the

                                 -50-

<PAGE>


Stock Option Agreement and (C) ARCO concurrently enters into a definitive
agreement to implement such ARCO Acquisition Proposal, or (iii) there shall be a
breach by BP Amoco of any representation, warranty, covenant or agreement
contained in this Agreement which would result in a failure of a condition set
forth in Section 4.3.1 or 4.3.2 and cannot be or is not cured prior to the
Termination Date.

         5.5. Effect of Termination and Abandonment.

         5.5.1.  In the event of termination of this Agreement and the
     abandonment of the Merger pursuant to this Article V, this Agreement (other
     than as set forth in Section 6.1) shall become void and of no effect with
     no liability on the part of either Party (or of any of its
     Representatives); provided, however, that no such termination shall relieve
     either Party of any liability for damages resulting from any willful breach
     of this Agreement or from any obligation to pay, if applicable, the amounts
     payable pursuant to Section 5.5.2 or 5.5.3.

         5.5.2. In the event that (i) this Agreement is terminated by either BP
     Amoco or ARCO pursuant to Section 5.2(iii) and at the time of the ARCO
     Stockholders Meeting (or at any adjournment thereof) an ARCO Acquisition
     Proposal exists or (ii) (A) this Agreement is terminated by either BP Amoco
     or ARCO pursuant to Section 5.2(iii) and prior to such termination ARCO's
     board of directors shall have withdrawn its approval or favorable
     recommendation to its stockholders of this Agreement, (B) this Agreement is
     terminated by BP Amoco pursuant to Section 5.3(i), Section 5.3(ii) (solely
     with respect to the recommendation by ARCO or the board of directors of
     ARCO of an ARCO Acquisition Proposal) or Section 5.3(iii) (solely with
     respect to a willful breach of Section 3.2), or (C) this Agreement is
     terminated by ARCO in accordance with Section 5.4(ii), then ARCO shall
     promptly, but in no event later than two business days after the date of
     such termination or, in the case of termination pursuant to Section
     5.4(ii), at the time provided therein, pay to BP Amoco as compensation for
     the Merger not becoming effective a termination payment equal to the ARCO
     Termination Amount (as defined below), which amount shall be exclusive of
     any expenses to be paid pursuant to Section 3.9, payable by wire transfer
     of same day funds. The term "ARCO Termination Amount" shall mean, in the
     case of termination by BP Amoco pursuant to clause (ii) of the preceding
     sentence, $450,000,000 (inclusive of value added tax, if any) or, in the
     case of termination by BP Amoco or ARCO pursuant to clause (i) of the
     preceding sentence, "ARCO Termination Amount" shall mean $250,000,000
     (inclusive of value added tax, if any), plus, if (x) ARCO executes and
     delivers an agreement with respect to any ARCO Acquisition Proposal (an
     "ARCO Alternative Agreement") or (y) an ARCO Acquisition Proposal with
     respect to ARCO is consummated, in any such case, within 12 months from the
     date of termination, an additional $200,000,000



                                      -51-

<PAGE>



     (inclusive of value added tax, if any) (which additional amount shall be
     paid promptly by wire transfer in same day funds, and in no event later
     than two business days after the earliest date on which the event requiring
     ARCO to pay such additional sum occurs). In the event that the board of
     directors of ARCO recommends the acceptance by ARCO stockholders of a
     third-party tender or exchange offer for the ARCO Common Shares, such
     recommendation shall be treated for purposes of this Section as though an
     ARCO Alternative Agreement had been executed. ARCO acknowledges that the
     agreements contained in this Section 5.5.2 are an integral part of the
     transactions contemplated by this Agreement, and that, without these
     agreements, BP Amoco would not enter into this Agreement; accordingly, if
     ARCO fails promptly to pay any amount due pursuant to this Section 5.5.2,
     and, in order to obtain such payment, BP Amoco commences a suit which
     results in a judgment against ARCO for the payment set forth in this
     Section 5.5.2, ARCO shall pay to BP Amoco its costs and expenses (including
     attorneys' fees) in connection with such suit, together with interest on
     the ARCO Termination Amount from each date for payment until the date of
     such payment at the prime rate of Citibank N.A. in effect on the date such
     payment was required to be made plus 2 percent.

         5.5.3. In the event that this Agreement is terminated (i) by ARCO
     pursuant to Section 5.4(i) or (ii) by either BP Amoco or ARCO pursuant to
     Section 5.2(iv) and prior to such termination BP Amoco's board of directors
     shall have withdrawn its approval or favorable recommendation to
     shareholders of the Merger, then BP Amoco shall promptly, but in no event
     later than two business days after the date of such termination, pay to
     ARCO a termination payment equal to the BP Amoco Termination Amount (as
     defined below), which amount shall be exclusive of any expenses to be paid
     pursuant to Section 3.9 payable by wire transfer of same day funds. The
     term "BP Amoco Termination Amount" shall mean $500,000,000 (inclusive of
     value added tax, if any). BP Amoco acknowledges that the agreements
     contained in this Section 5.5.3 are an integral part of the transactions
     contemplated by this Agreement, and that, without these agreements, ARCO
     would not enter into this Agreement; accordingly, if BP Amoco fails
     promptly to pay any amount due pursuant to this Section 5.5.3, and, in
     order to obtain such payment, ARCO commences a suit which results in a
     judgment against BP Amoco for the payment set forth in this Section 5.5.3,
     BP Amoco shall pay to ARCO its costs and expenses (including attorneys'
     fees) in connection with such suit, together with interest on the BP Amoco
     Termination Amount from each date for payment until the date of such
     payment at the prime rate of Citibank N.A. in effect on the date such
     payment was required to be made plus 2 percent.



                                      -52-

<PAGE>


                                   ARTICLE VI

                            Miscellaneous and General

         6.1. Survival. This Article VI and the agreements of BP Amoco and ARCO
contained in Article I, Sections 3.8 (Benefits and Other Matters), 3.15
(Accounting Matters) and Section 3.16 (Tax Matters) shall survive the Effective
Time. This Article VI, the representations and warranties contained in Section
2.1.3 (Corporate Authority; Approval and Fairness), the agreements of BP Amoco
and ARCO contained in Section 3.7 (Publicity), Section 3.9 (Expenses), Section
5.5 (Effect of Termination and Abandonment), and the last sentence of Section
3.6 (Access) shall survive the termination of this Agreement. All other
representations, warranties, agreements and covenants in this Agreement shall
not survive the Effective Time or the termination of this Agreement.

         6.2. Modification or Amendment. This Agreement may be modified or
amended by agreement of the Parties, by action taken or authorized by their
respective boards of directors, at any time prior to the Effective Time;
provided, however, that, after approval by ARCO stockholders of the matters
presented at the ARCO Stockholders Meeting, no modification or amendment shall
be made which under applicable Law requires further approval by such
stockholders without such further approval. This Agreement may not be modified
or amended except by an instrument in writing executed and delivered by duly
authorized officers of each of the Parties.

         6.3. Waiver. Any provision of this Agreement may be waived prior to the
Effective Time if, and only if, such waiver is in writing and signed by the
Party against whom the waiver is to be effective.

         6.4. Failure or Indulgence Not Waiver; Remedies Cumulative. No failure
or delay by any Party in exercising any right, power or privilege hereunder
shall operate as a waiver thereof, nor shall any single or partial exercise
thereof preclude any other or further exercise thereof or the exercise of any
other right, power or privilege. Except as otherwise herein provided, the rights
and remedies herein provided shall be cumulative and not exclusive of any rights
or remedies provided by Law.

         6.5. Counterparts. This Agreement may be executed in any number of
counterparts, each such counterpart being deemed to be an original instrument,
and all such counterparts shall together constitute the same agreement.


                                      -53-

<PAGE>



         6.6.   GOVERNING LAW AND VENUE; WAIVER OF JURY TRIAL.

         6.6.1. THIS AGREEMENT SHALL BE DEEMED TO BE MADE IN, AND IN ALL 
     RESPECT SHALL BE INTERPRETED, CONSTRUED AND GOVERNED BY AND IN ACCORDANCE
     WITH THE LAWS OF THE STATE OF DELAWARE APPLICABLE TO CONTRACTS TO BE
     PERFORMED WHOLLY IN SUCH STATE, EXCEPT TO THE EXTENT THAT IN THE CASE OF BP
     AMOCO, THE COMPANIES ACT AND ENGLISH LAW ARE APPLICABLE. The Parties hereby
     irrevocably submit to the jurisdiction of the federal courts of the United
     States of America located in the State of Delaware and the state courts of
     the State of Delaware, solely in respect of the interpretation and
     enforcement of the provisions of this Agreement and in respect of the
     transactions contemplated hereby and hereby waive, and agree not to assert,
     as a defense in any action, suit or proceeding for the interpretation or
     enforcement hereof, that it is not subject thereto or that such action,
     suit or proceeding may not be brought or is not maintainable in said courts
     or that the venue thereof may not be appropriate or that this Agreement may
     not be enforced in or by such courts, and the Parties irrevocably agree
     that all claims with respect to such action or proceeding shall be heard
     and determined in such a court. The Parties hereby consent to and grant any
     such court jurisdiction over the person of such Parties and over the
     subject matter of such dispute and agree that mailing of process or other
     papers in connection with any such action or proceeding in the manner
     provided in Section 6.7, or in such other manner as may be permitted by
     Law, shall be valid and sufficient service thereof.

         6.6.2. EACH PARTY ACKNOWLEDGES AND AGREES THAT ANY CONTROVERSY WHICH
     MAY ARISE UNDER THIS AGREEMENT IS LIKELY TO INVOLVE COMPLICATED AND
     DIFFICULT ISSUES, AND THEREFORE EACH SUCH PARTY HEREBY IRREVOCABLY AND
     UNCONDITIONALLY WAIVES ANY RIGHT SUCH PARTY MAY HAVE TO A TRIAL BY JURY IN
     RESPECT OF ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING
     TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED BY THIS AGREEMENT. EACH
     PARTY CERTIFIES AND ACKNOWLEDGES THAT (i) NO REPRESENTATIVE, AGENT OR
     ATTORNEY OF ANY OTHER PARTY HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT
     SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE
     FOREGOING WAIVER, (ii) EACH SUCH PARTY UNDERSTANDS AND WITH THE ADVICE OF
     COUNSEL HAS CONSIDERED THE IMPLICATIONS OF THIS WAIVER, (iii) EACH SUCH
     PARTY MAKES THIS WAIVER VOLUNTARILY, AND (iv) EACH SUCH


                                      -54-

<PAGE>


     PARTY HAS BEEN INDUCED TO ENTER INTO THIS AGREEMENT BY, AMONG OTHER THINGS,
     THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION 6.6.

         6.7. Notices. Notices, requests, instructions or other documents to be
given under this Agreement shall be in writing and shall be deemed given, (i)
when sent if sent by facsimile, provided that the facsimile is promptly
confirmed by telephone confirmation thereof, (ii) when delivered, if delivered
personally to the intended recipient, and (iii) one business day later, if sent
by overnight delivery via a national courier service, and in each case,
addressed to a Party at the following address for such Party:

            if to ARCO:

            ARCO

            Atlantic Richfield Company
            333 South Hope Street
            Los Angeles, California  90071
            Attention:    Bruce Whitmore, Esq.
            Telecopier:   213-486-1818

            with copies to

            Cravath, Swaine & Moore
            Worldwide Plaza
            825 Eighth Avenue
            New York, New York  10019
            Attention:    Richard Hall, Esq.
            Telecopier:   (212) 474-3700

            and

            Clifford Chance
            200 Aldersgate Street
            London EC1A 4J5
            England
            Attention:    Adam Signy, Esq.
            Telecopier:   44-171-600-5555


                                      -55-

<PAGE>



            if to BP Amoco or Merger Sub:

            BP Amoco p.l.c.
            Brittanic House
            1 Finsbury Circus
            London EC2M 7BA
            England
            Attention:    Peter B.P. Bevan, Esq.
                          General Counsel
            Telecopier:   44-171-496-4592

            with copies to

            Sullivan & Cromwell
            125 Broad Street
            New York, New York  10004
            Attention:    Benjamin F. Stapleton, Esq.
            Telecopier:   (212) 558-3588

            and

            Linklaters & Paines
            One Silk Street
            London EC2Y 8HQ
            Attention:    David Cheyne, Esq.
            Telecopier:   011-44-171-456-2222

or to such other Persons or addresses as may be designated in writing by the
Party to receive such notice as provided above.

         6.8. Entire Agreement. This Agreement (including any exhibits hereto),
the Stock Option Agreement and the Confidentiality Agreement constitute the
entire agreement, and supersede all other prior agreements, understandings,
representations and warranties both written and oral, between the Parties with
respect to the subject matter hereof. References herein to this Agreement shall
for all purposes be deemed to include references to the BP Amoco Disclosure
Letter and the ARCO Disclosure Letter. Except as set forth in Sections 1.3, 1.5
and 3.8 (except for the provisions of Section 3.8.1.1 and 3.8.1.2), this
Agreement is not intended to confer upon any Person other than the Parties any
rights or remedies hereunder. EACH PARTY HERETO AGREES THAT, EXCEPT FOR THE
REPRESENTATIONS AND WARRANTIES CONTAINED IN THIS AGREEMENT, THE STOCK OPTION
AGREEMENT OR ANY OTHER


                                      -56-

<PAGE>


AGREEMENT CONTEMPLATED HEREBY OR THEREBY, NONE OF BP AMOCO, ARCO OR MERGER SUB
MAKES ANY OTHER REPRESENTATIONS OR WARRANTIES, AND EACH HEREBY DISCLAIMS ANY
OTHER REPRESENTATIONS OR WARRANTIES MADE BY ITSELF OR ANY OF ITS OFFICERS,
DIRECTORS, EMPLOYEES, AGENTS, FINANCIAL AND LEGAL ADVISORS OR OTHER
REPRESENTATIVES WITH RESPECT TO THE EXECUTION AND DELIVERY OF THIS AGREEMENT,
THE STOCK OPTION AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY,
NOTWITHSTANDING THE DELIVERY OR DISCLOSURE TO THE OTHER OR THE OTHER'S
REPRESENTATIVES OF ANY DOCUMENTATION OR OTHER INFORMATION WITH RESPECT TO ANY
ONE OR MORE OF THE FOREGOING.

         6.9. Obligations of BP Amoco and of ARCO. Whenever this Agreement
requires a Subsidiary of BP Amoco to take any action, such requirement shall be
deemed to include an undertaking on the part of BP Amoco to use best reasonable
efforts to cause such Subsidiary to take such action. Subject to Section 3.17,
whenever this Agreement requires a Subsidiary of ARCO to take any action, such
requirement shall be deemed to include an undertaking on the part of ARCO to use
best reasonable efforts to cause such Subsidiary to take such action.

         6.10. Severability. The provisions of this Agreement shall be deemed
severable and the invalidity or unenforceability of any provision shall not
affect the validity or enforceability of the other provisions hereof. If any
provision of this Agreement, or the application thereof to any Person or any
circumstance, is invalid or unenforceable, (a) a suitable and equitable
provision shall be substituted therefor in order to carry out, so far as may be
valid and enforceable, the intent and purpose of such invalid or unenforceable
provision unless the substitution of such provision would materially frustrate
the express intent and purposes of this Agreement, and (b) the remainder of this
Agreement and the application of such provision to other Persons or
circumstances shall not be affected by such invalidity or unenforceability, nor
shall such invalidity or unenforceability affect the validity or enforceability
of such provision, or the application thereof, in any other jurisdiction.

         6.11. Interpretation. The headings herein are for convenience of
reference only, do not constitute part of this Agreement and shall not be deemed
to limit or otherwise affect any of the provisions hereof. Where a reference in
this Agreement is made to a Section or Exhibit, such reference shall be to a
Section of or Exhibit to this Agreement unless otherwise indicated. Whenever the
words "include," "includes" or "including" are used in this Agreement, they
shall be deemed to be followed by the words "without limitation."


                                      -57-

<PAGE>



         6.12. Assignment. This Agreement shall not be assignable by operation
of law or otherwise, and any purported assignment in violation of this provision
shall be void.


                                      -58-

<PAGE>



         IN WITNESS WHEREOF, this Agreement has been duly executed and delivered
by the duly authorized officers of BP Amoco, ARCO and Merger Sub as of the date
hereof.


                              BP AMOCO p.l.c.

                              By:   /s/  John Browne                      
                                  ----------------------------------------
                                  Name:  (E.J.P. Browne) - Sir John Browne
                                  Title: Chief Executive Officer


                              By:   /s/  B.E. Grote                       
                                  ----------------------------------------
                                  Name:  B.E. Grote
                                  Title: Executive Vice President


                              ATLANTIC RICHFIELD COMPANY

                              By:   /s/  Mike R. Bowlin                  
                                  ----------------------------------------
                                  Name:  Mike R. Bowlin
                                  Title: Chairman of the Board and
                                         Chief Executive Officer


                              PRAIRIE HOLDINGS, INC.

                              By:   /s/  Peter B.P. Bevan               
                                  ----------------------------------------
                                  Name:  P.B.P. Bevan
                                  Title: President



                                      -59-


                                                                       EXHIBIT 2



         STOCK OPTION AGREEMENT, dated as of the 31st day of March, 1999 (this
"Agreement"), between Atlantic Richfield Company, a Delaware corporation
("Issuer"), and BP Amoco p.l.c., an English public limited company (including
any assigns permitted under Section 11 hereof, "Grantee").


                                    RECITALS

         A. The Merger Agreement. Contemporaneously with the entry into this
Agreement and the grant of the Option (as defined in Section 1(a)), Issuer,
Grantee, and Prairie Holdings, Inc., a Delaware corporation and a wholly-owned
subsidiary of Grantee ("Merger Sub"), are entering into an Agreement and Plan of
Merger, dated as of the date hereof (the "Merger Agreement"), pursuant to which
Grantee and Issuer intend to effect the Merger (as defined in the Merger
Agreement).

         B. The Stock Option Agreement. As an inducement and condition to
Grantee's willingness to enter into the Merger Agreement, and in consideration
thereof, the board of directors of Issuer has approved the grant to Grantee of
the Option pursuant to this Agreement and the acquisition of Common Stock (as
defined below) by Grantee pursuant to this Agreement; provided, that such grant
was expressly conditioned upon, and made to have no effect until after,
execution and delivery by Issuer, Grantee and Merger Sub of the Merger
Agreement.

         C. Capitalized Terms. Capitalized terms used herein but not defined
herein shall have the meanings ascribed to such terms in the Merger Agreement.

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements set forth herein and in the Merger Agreement, the
parties hereto agree as follows:

         1. The Option. (a) Issuer hereby grants to Grantee an unconditional,
irrevocable option (the "Option") to purchase, subject to the terms hereof, up
to 64,861,617 fully paid and nonassessable shares ("Option Shares") of common
stock, par value $2.50 per share, of Issuer ("Common Stock") at a price per
share in cash equal to $82.82 (subject to adjustment in accordance with this
Agreement, the "Option Price"); provided, however, that in no event shall the
number of Option Shares exceed 19.9% of the shares of Common Stock issued and
outstanding at the time of exercise (without giving effect to the Option Shares
issued or issuable under the Option) (the "Maximum Applicable


<PAGE>



Percentage"). The number of Option Shares purchasable upon exercise of the
Option and the Option Price are subject to adjustment as set forth herein.

         (b) In the event that any additional shares of Common Stock are issued
or otherwise become outstanding after the date of this Agreement (other than
pursuant to this Agreement), the aggregate number of Option Shares purchasable
upon exercise of the Option shall automatically be increased (without any
further action on the part of Issuer or Grantee being necessary) so that, taking
into consideration any such issuance, such aggregate number equals the Maximum
Applicable Percentage.

         (c) The Option Price with respect to the Option Shares as to which
Grantee may propose to exercise this Option pursuant to Section 2, or to request
the repurchase of this Option by Issuer pursuant to Section 9 (in either case,
the "Proposed Exercise Shares"), shall not be greater than, and shall be
adjusted downward to the extent necessary to be, the Maximum Option Price (as
defined below). The "Maximum Option Price" with respect to any Proposed Exercise
Shares shall be that price per share in cash at which the Option must be
exercisable in order to result in a Total Profit (as defined in Section 19) to
Grantee, determined as of the date of such proposal, of $25,000,000, assuming
for such purpose that this Option were exercised on such date for all of the
Option Shares subject to this Option and that all of such Option Shares were
sold for cash at the closing market price on the New York Stock Exchange, Inc.
(the "NYSE") for the Common Stock as of the close of business on the preceding
trading day (less customary brokerage commissions); provided that the Maximum
Option Price may not be less than the par value per share of the Common Stock.

         2. Exercise; Closing. (a) Conditions to Exercise; Termination. Grantee
may exercise the Option, in whole but not in part (except as provided in Section
14 and Section 19), by giving a written notice thereof as provided in Section
2(d) within 180 days following the occurrence of a Triggering Event (as defined
in Section 2(b)) unless prior to the giving of such notice the Effective Time
(as defined in the Merger Agreement) shall have occurred. The Option shall
terminate upon either (i) the occurrence of the Effective Time or (ii) the close
of business on the earlier of (x) the date 180 days after the date on which a
Triggering Event occurs and (y) the date on which it is no longer possible for a
Triggering Event to occur, provided


                                        2
<PAGE>



that no Triggering Event shall have occurred prior to or upon such date.

         (b) Triggering Event. A "Triggering Event" shall have occurred if the
Merger Agreement is terminated and Grantee then or thereafter becomes entitled
to receive an aggregate of $450,000,000 (taking into account any amounts to
which Grantee will have theretofore become entitled) as the ARCO Termination
Amount pursuant to Section 5.5.2 of the Merger Agreement.

         (c) Notice of Triggering Event by Issuer. Issuer shall notify Grantee
promptly in writing of the occurrence of any Triggering Event and the number of
shares of Common Stock issued and outstanding as of the date of such notice, it
being understood that the giving of such notice by Issuer shall not be a
condition to the right of Grantee to exercise the Option.

         (d) Notice of Exercise by Grantee. If Grantee shall be entitled to and
wishes to exercise the Option, it shall send to Issuer a written notice (an
"Exercise Notice" and the date of which is referred to herein as the "Notice
Date") specifying (i) the total amount payable to Issuer on the exercise of the
Option in respect of the Option Shares and (ii) a place and date (the "Closing
Date") not earlier than three business days nor later than 60 business days from
the Notice Date for the closing of such purchase (the "Closing"); provided, that
if a filing is required under the Hart-Scott-Rodino Antitrust Improvements Act
of 1976, as amended (the "HSR Act"), or prior notification to or application for
approval of any other regulatory authority in the U.S., U.K. or elsewhere is
required in connection with such purchase, Grantee and Issuer, as required,
promptly after the giving of the Exercise Notice shall file any and all required
notices, applications or other documents necessary for approval and shall
expeditiously process the same and in such event the period of time referred to
in clause (ii) shall commence on the date on which Grantee furnishes to Issuer a
supplemental written notice setting forth the Closing Date, which notice shall
be furnished as promptly as practicable after all required notification periods
shall have expired or been terminated and all required approvals shall have been
obtained and all requisite waiting periods shall have passed. Each of Grantee
and the Issuer agrees to use its best reasonable efforts to cooperate with and
provide information to Issuer or Grantee, as the case may be, with respect to
any required


                                        3
<PAGE>



filing, notice or application for approval to such regulatory authority.

         (e) Payment of Purchase Price. At the Closing, Grantee shall pay to
Issuer the aggregate Option Price for the Option Shares in immediately available
funds by a wire transfer to a bank account designated by Issuer; provided, that
failure or refusal of Issuer to designate such a bank account shall not preclude
Grantee from exercising the Option.

         (f) Delivery of Common Stock. At the Closing, simultaneously with the
payment of the purchase price by Grantee, Issuer shall deliver to Grantee or
such other Person as Grantee may nominate in writing, a certificate or
certificates representing the number of Option Shares purchased by Grantee. If
at the time of issuance of the Option Shares hereunder, Issuer shall have issued
any rights or other securities which are attached to or otherwise associated
with the Common Stock, then each Option Share shall also represent such rights
or other securities with terms substantially the same as, and at least as
favorable to Grantee as, are provided under any shareholder rights agreement or
similar agreement of Issuer then in effect.

         (g) Resale Restriction. The Grantee will not sell or transfer any
Option Shares or other securities acquired by Grantee upon exercise of the
Option except pursuant to an effective registration statement under the
Securities Act of 1933, as amended (the "Securities Act"), or in a transaction
exempt from registration under the Securities Act. Each certificate for Common
Stock delivered at the Closing may be endorsed with a restrictive legend that
shall read substantially as follows:

         "The transfer of the shares represented by this certificate
     is subject to resale restrictions arising under the Securities
     Act of 1933, as amended."

It is understood and agreed that the above legend shall be removed by delivery
of substitute certificate(s) without such reference if Grantee shall have
delivered to Issuer a copy of a letter from the staff of the Securities and
Exchange Commission, or a written opinion of counsel, in form and substance
reasonably satisfactory to Issuer, to the effect that such legend is not
required for purposes of the Securities Act. In addition, such certificate or


                                        4
<PAGE>



certificates shall bear any other legend as may be required by applicable law.

         (h) Ownership of Record; Tender of Purchase Price; Expenses. Upon the
tender of the applicable purchase price in immediately available funds
(following the giving of the Exercise Notice) at the Closing, Grantee shall be
deemed to be the holder of record of the shares of Common Stock issuable upon
such exercise, notwithstanding that the stock transfer books of Issuer may then
be closed or that a certificate or certificates representing such shares of
Common Stock may not have been delivered to Grantee. Issuer shall pay all
expenses, and any and all federal, national, state, provincial and local taxes
and other charges worldwide that may be payable in connection with the
preparation, issuance and delivery of stock certificates under this Section 2 in
the name of Grantee or its nominee, assignee, transferee or designee.

         3. Covenants of Issuer. In addition to its other agreements and
covenants herein, Issuer agrees:

         (a) Shares Reserved for Issuance. To maintain, free from preemptive
     rights, sufficient authorized but unissued or treasury shares of Common
     Stock so that the Option may be fully exercised without additional
     authorization of Common Stock after giving effect to all other options,
     warrants, convertible securities and other rights of third parties to
     purchase shares of Common Stock from Issuer, and to issue the appropriate
     number of shares of Common Stock pursuant to the terms of this Agreement;

         (b) No Avoidance. Not to avoid or seek to avoid (whether by charter
     amendment or through reorganization, consolidation, merger, issuance of
     rights, dissolution or sale of assets, or by any other voluntary act) the
     observance or performance of any of the covenants, agreements or conditions
     to be observed or performed hereunder by Issuer; and

         (c) Further Assurances. Promptly after the date hereof to take all
     actions as may from time to time be required (including (i) complying with
     all applicable premerger notification, reporting and waiting period
     requirements under the HSR Act and (ii) in the event that prior filing
     with, notification to or approval of any other regulatory authority in the
     U.S., U.K. or elsewhere is necessary before the Option may be


                                       5
<PAGE>



     exercised, cooperating fully with Grantee in preparing and processing the
     required filings, notices or applications) in order to permit Grantee to
     exercise the Option, to purchase Option Shares pursuant to such exercise
     and otherwise to exercise Grantee's rights under this Agreement and to take
     all action necessary to protect the rights of Grantee against dilution.

         4. Representations and Warranties of Issuer. Issuer hereby represents
and warrants to Grantee as follows:

         (a) Merger Agreement. Issuer hereby makes each of the representations
     and warranties contained in Sections 2.1.2.2 and 2.1.4 of the Merger
     Agreement as they relate to Issuer and this Agreement, as if such
     representations and warranties were set forth herein.

         (b) Shares Reserved for Issuance; Capital Stock. The Option Shares
     issuable in accordance with the terms of this Agreement have been duly
     reserved for issuance by Issuer and upon any issuance of such shares in
     accordance with the terms hereof, such Option Shares will be duly
     authorized, validly issued, fully paid and nonassessable, and will be
     delivered free and clear of any lien, pledge, security interest, claim or
     other encumbrance (other than those created by this Agreement) and not
     subject to any preemptive rights.

         (c) Corporate Authority. Issuer has all requisite corporate power and
     authority and has taken all corporate action necessary in order to execute,
     deliver and perform its obligations under this Agreement and to consummate
     the transactions contemplated hereby; the execution and delivery of this
     Agreement have been duly authorized by all necessary corporate action on
     the part of Issuer, and, assuming the due authorization, execution and
     delivery of this Agreement by Grantee, this Agreement constitutes a valid
     and binding agreement of Issuer enforceable against Issuer in accordance
     with its terms, subject to bankruptcy, insolvency, fraudulent transfer,
     reorganization, moratorium and similar laws of general applicability
     relating to or affecting creditors' rights and to general equity
     principles.

         (d) Takeover Statutes. Assuming that Grantee's representation and
     warranty in Section 2.1.10.1 of the Merger Agreement is true and correct,
     Issuer's board of directors has taken all appropriate and necessary


                                       6
<PAGE>


     actions such that Section 203 of the DGCL is inapplicable to the execution
     and delivery of this Agreement and to the consummation of the transactions
     contemplated hereby. No other "fair price," "moratorium," "control share
     acquisition" or other similar anti-takeover statute or regulation (each a
     "Takeover Statute") as in effect on the date hereof is applicable to the
     execution and delivery of this Agreement, the Common Stock issuable
     hereunder or to the other transactions contemplated by this Agreement. No
     anti-takeover provision contained in Issuer's certificate of incorporation
     or its by-laws prohibits or restricts the execution and delivery of this
     Agreement or, at the time of any exercise of the Option, will prohibit or
     restrict the issuance of Common Stock hereunder or the consummation of the
     other transactions contemplated by this Agreement.

         5. Representations and Warranties of Grantee. Grantee hereby represents
and warrants to Issuer that Grantee has all requisite corporate power and
authority and has taken all corporate action necessary in order to execute,
deliver and perform its obligations under this Agreement and to consummate the
transactions contemplated hereby; the execution and delivery of this Agreement
have been duly authorized by all necessary corporate action on the part of
Grantee, and, assuming the due authorization, execution and delivery of this
Agreement by Issuer, constitutes a valid and binding agreement of Grantee
enforceable against Grantee in accordance with its terms, subject to bankruptcy,
insolvency, fraudulent transfer, reorganization, moratorium and similar laws of
general applicability relating to or affecting creditors' rights and to general
equity principles.

         6.  Replacement. Upon (i) receipt by Issuer of evidence reasonably
satisfactory to it of the loss, theft, destruction, or mutilation of this
Agreement, (ii) receipt by Issuer of reasonably satisfactory indemnification in
the case of loss, theft or destruction and (iii) surrender and cancellation of
this Agreement in the case of mutilation, Issuer will execute and deliver a new
Agreement of like tenor and date. Any such new Agreement executed and delivered
shall constitute an additional contractual obligation on the part of Issuer,
whether or not the Agreement so lost, stolen, destroyed or mutilated shall at
any time be enforceable by any Person other than the holder of the new
Agreement.


                                       7
<PAGE>



         7.  Adjustments.  In addition to the adjustment to the total number of
Option Shares pursuant to Section 1(b) and the adjustment to the Option Price
pursuant to Section 1(c), the total number of Option Shares purchasable upon the
exercise of the Option hereof and the Option Price shall be subject to
adjustment from time to time as follows:

         (a) In the event of any change in the outstanding shares of Common
     Stock by reason of stock dividends, splits, combinations, subdivisions or
     reclassifications, mergers, recapitalizations, extraordinary dividends or
     distributions, exchanges of shares or the like, the type and number of
     Option Shares purchasable upon exercise of the Option shall be
     appropriately adjusted, and proper provision shall be made in the
     agreements governing any such transaction, so that (i) Grantee shall
     receive upon exercise of the Option the number and class of shares, other
     securities, property or cash that Grantee would have received in respect of
     the Option Shares purchasable upon exercise of the Option if the Option had
     been exercised and such Option Shares had been issued to Grantee
     immediately prior to such event or the record date therefor, as applicable;
     and (ii) in the event any additional shares of Common Stock are to be
     issued or otherwise become outstanding as a result of any such change
     (other than pursuant to an exercise of the Option), the number of Option
     Shares purchasable upon exercise of the Option shall be increased so that,
     after such issuance the number of Option Shares so purchasable equals the
     Maximum Applicable Percentage of the number of shares of Common Stock
     issued and outstanding immediately after the consummation of such change;
     and

         (b) Whenever the number of Option Shares purchasable upon exercise
     hereof is adjusted as provided in this Section 7, the Option Price shall
     be adjusted by multiplying the Option Price by a fraction, the numerator of
     which is equal to the number of Option Shares purchasable prior to the
     adjustment and the denominator of which is equal to the number of Option
     Shares purchasable after the adjustment.

            8. Registration. (a) Upon the occurrence of a Triggering Event,
Issuer shall, at the request of Grantee included in the Exercise Notice, as
promptly as practicable prepare, file and keep current a shelf registration
statement under the Securities Act covering all Option Shares


                                       8
<PAGE>



issued and issuable pursuant to the Option and shall use its best efforts to
cause such registration statement to become effective and remain current in
order to permit the sale or other disposition of any Option Shares issued upon
exercise of the Option in accordance with any plan of disposition requested by
Grantee; provided, however, that Issuer may postpone the filing of a
registration statement relating to a registration request by Grantee under this
Section 8 for a period of time (not in excess of 30 days) if in its judgment
such filing would require the disclosure of material information that Issuer has
a bona fide business purpose for preserving as confidential. Issuer will use its
best efforts to cause such registration statement first to become effective and
then to remain effective for 270 days from the day such registration statement
first becomes effective or until such earlier date as all shares registered
shall have been sold by Grantee. In connection with any such registration,
Issuer and Grantee shall provide each other with representations, warranties,
indemnities, contribution and other agreements customarily given in connection
with such registrations. If requested by Grantee in connection with such
registration, Issuer shall become a party to any underwriting agreement relating
to the sale of such shares, but only to the extent of obligating Issuer in
respect of representations, warranties, indemnities, contribution and other
agreements customarily made by issuers in such underwriting agreements.

         (b) In the event that Grantee so requests, the closing of the sale or
other disposition of the Option Shares or other securities pursuant to a
registration statement filed pursuant to Section 8(a) shall occur substantially
simultaneously with the exercise of the Option.

         9. Repurchase of Option and/or Shares. (a) Repurchase; Repurchase
Price. At the request of Grantee, given in writing within 180 days following the
occurrence of a Triggering Event (or such later period as is provided in Section
2(d) with respect to any required filing, notice or application for approval or
pursuant to a request by Grantee in accordance with Section 10), (i) Issuer
shall repurchase the Option from Grantee, in whole but not in part (except as
provided in Section 9(c) and Section 19), at a price (the "Option Repurchase
Price") equal to the number of Option Shares then purchasable upon exercise of
the Option multiplied by the amount by which the Market Price (as defined below)
exceeds the applicable Option Price (giving effect to the Maximum Option Price)
or


                                       9
<PAGE>



(ii) Issuer shall repurchase all Option Shares then owned by Grantee at a price
(the "Option Share Repurchase Price") equal to the number of such Option Shares
multiplied by the Market Price; provided, however, that the Option Repurchase
Price or the Option Share Repurchase Price, as the case may be, shall be reduced
to the extent necessary for it not to exceed the maximum amount for which Issuer
is permitted, without a vote of the stockholders of Issuer, to repurchase the
Option or Option Shares, as the case may be, on the date of repurchase in
accordance with the provisions of Article VII of the certificate of
incorporation of Issuer. The term "Market Price" shall mean, for any share of
Common Stock, the average of the closing sale prices during the 90-day period
immediately preceding the delivery of the Repurchase Notice on the Composite
Tape for NYSE-listed stocks, or, if the Common Stock is not quoted on the
Composite Tape, on the NYSE, or if the Common Stock is not listed on the NYSE,
on the principal United States securities exchange registered under the
Securities Exchange Act of 1934 on which the Common Stock is listed, or if the
Common Stock is not listed on any such exchange, the average of the closing bid
quotations with respect to a share of Common Stock during the 90-day period
immediately preceding the date of the Repurchase Notice on the National
Association of Securities Dealers, Inc. Automated Quotations System or any
system then in use, or if no such quotations are available, the Market Price on
the date of the Repurchase Notice of a share of Common Stock, as determined by
the Board of Directors of Issuer in good faith.

         (b) Method of Repurchase. Grantee may exercise its right to require
Issuer to repurchase the Option, in whole but not in part, or all Option Shares
then owned by Grantee pursuant to this Section 9 by surrendering for such
purpose to Issuer, at its principal office, this Agreement or certificates for
such Option Shares, as applicable, accompanied by a written notice or notices
stating that Grantee elects to require Issuer to repurchase the Option or such
Option Shares in accordance with the provisions of this Section 9 (such notice,
a "Repurchase Notice"). As promptly as practicable, and in any event within 15
business days after the surrender of this Agreement or a certificate or
certificates representing Option Shares and the receipt of the Repurchase Notice
relating thereto, Issuer shall deliver or cause to be delivered to Grantee the
applicable Option Repurchase Price or the Option Share Repurchase Price.

         (c) Effect of Statutory or Regulatory Restraints on Repurchase. To the
extent that, upon or following the


                                       10
<PAGE>



giving of a Repurchase Notice, Issuer is prohibited under applicable law or
regulation from repurchasing the Option or any Option Shares subject to such
Repurchase Notice (and Issuer hereby undertakes to use its best efforts to
obtain all required regulatory and legal approvals and to file any required
notices as promptly as practicable in order to accomplish such repurchase),
Issuer shall immediately so notify Grantee in writing and thereafter deliver or
cause to be delivered, from time to time, to Grantee the portion of the Option
Repurchase Price or the Option Share Repurchase Price that Issuer is no longer
prohibited from delivering, within 2 business days after the date on which it is
no longer so prohibited; provided, however, that upon notification by Issuer in
writing of such prohibition, Grantee may, within 5 days of receipt of such
notification from Issuer, revoke in writing its Repurchase Notice, whether in
whole or to the extent of the prohibition, whereupon, in the latter case, Issuer
shall promptly (i) deliver to Grantee that portion of the Option Repurchase
Price or the Option Share Repurchase Price that Issuer is not prohibited from
delivering; and (ii) deliver to Grantee, as appropriate, (A) with respect to the
Option, a new stock option agreement evidencing the right of Grantee to purchase
that number of Option Shares for which the surrendered stock option agreement
was exercisable at the time of delivery of the Repurchase Notice less the number
of shares as to which the Option Repurchase Price has theretofore been delivered
to Grantee, or (B) with respect to Option Shares, a certificate for the Option
Shares as to which the Option Share Repurchase Price has not theretofore been
delivered to Grantee. Notwithstanding anything to the contrary in this
Agreement, including, without limitation, the time limitations on the exercise
of the Option, Grantee may give notice of exercise of the Option for 180 days
after a notice of revocation has been issued pursuant to this Section 9(c) and
thereafter exercise the Option in accordance with the applicable provisions of
this Agreement.

         (d) Acquisition Transactions. In addition to any other restrictions or
covenants, Issuer hereby agrees that, in the event that Grantee delivers a
Repurchase Notice, it shall not enter or agree to enter into an agreement or
series of agreements relating to a merger with or into or the consolidation with
any other Person, the sale of all or substantially all of the assets of Issuer
or any similar transaction or disposition unless the other party or parties to
such agreement or agreements agree to assume in writing Issuer's obligations
under Section 9(a) and, notwithstanding any notice of revocation delivered
pursuant to the proviso


                                       11
<PAGE>



to Section 9(c), Grantee may require such other party or parties to perform
Issuer's obligations under Section 9(a) unless such party or parties are
prohibited by law or regulation from such performance, in which case such party
or parties shall be subject to the obligations of the Issuer under Section 9(c).

         10. Extension of Exercise Periods. The 180-day periods for exercise of
certain rights under Sections 2 and 9 shall be extended in each such case at the
request of Grantee to the extent necessary to avoid liability by Grantee under
Section 16(b) of the Exchange Act by reason of such exercise.

         11. Assignment. Neither party hereto may assign or delegate any of its
rights or obligations under this Agreement or the Option to any other Person
without the express written consent of the other party, except that this
Agreement or the Option may be assigned to any direct or indirect wholly owned
Subsidiary of Grantee. Any attempted assignment or delegation in contravention
of the preceding sentence shall be null and void.

         12. Filings; Other Actions. Each of Grantee and Issuer will use its
best efforts to make all filings with, notices to and applications for approval
of, and to obtain consents of, all third parties and governmental authorities
necessary for the consummation of the transactions contemplated by this
Agreement. Subject to applicable law and the rules and regulations of the NYSE,
the Issuer will promptly file an application to have the Option Shares listed on
the NYSE, subject to notice of issuance, and will use its best reasonable
efforts to obtain approval of such application; provided, that if the Issuer is
unable to effect such listing on the NYSE by the Closing Date, the Issuer will
nevertheless be obligated to deliver the Option Shares upon the Closing Date.

         13. Specific Performance. The parties hereto acknowledge that damages
would be an inadequate remedy for a breach of this Agreement by either party
hereto and that the obligations of the parties hereto shall be specifically
enforceable through injunctive or other equitable relief.

         14. Severability; Etc. The provisions of this Agreement shall be deemed
severable and the invalidity or unenforceability of any provision shall not
affect the validity or enforceability of the other provisions hereof. If any
provision of this Agreement, or the application


                                       12
<PAGE>



thereof to any Person or any circumstance, is invalid or unenforceable, (a) a
suitable and equitable provision shall be substituted therefor in order to carry
out, so far as may be valid and enforceable, the intent and purpose of such
invalid or unenforceable provision unless the substitution of such provision
would materially frustrate the express intent and purposes of this Agreement,
and (b) the remainder of this Agreement and the application of such provision to
other Persons or circumstances shall not be affected by such invalidity or
unenforceability, nor shall such invalidity or unenforceability affect the
validity or enforceability of such provision, or the application thereof, in any
other jurisdiction. If for any reason a court or regulatory agency determines
that Grantee is not permitted to acquire pursuant to Section 2 the full number
of Option Shares provided in Section 1(a) hereof (as adjusted pursuant to
Sections 1(b) and 7 hereof), it is the express intention of Issuer to allow
Grantee to acquire such lesser number of Option Shares as may be permissible,
without any amendment or modification hereof.

         15. Notices. Notices, requests, instructions or other documents to be
given under this Agreement shall be in writing and shall be deemed given (i)
when sent if sent by facsimile, provided that the facsimile is promptly
confirmed by telephone confirmation thereof, (ii) when delivered, if delivered
personally to the intended recipient, and (iii) one business day later, if sent
by overnight delivery via a national courier service, and in each case addressed
to a party at the respective addresses of the parties set forth in the Merger
Agreement.

         16. GOVERNING LAW; VENUE; WAIVER OF JURY TRIAL. THIS AGREEMENT SHALL BE
DEEMED TO BE MADE IN AND IN ALL RESPECTS SHALL BE INTERPRETED, CONSTRUED AND
GOVERNED BY AND IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE APPLICABLE
TO CONTRACTS TO BE PERFORMED WHOLLY IN SUCH STATE. The parties hereby
irrevocably submit to the jurisdiction of the Federal courts of the United
States of America located in the State of Delaware and the state courts of the
State of Delaware solely in respect of the interpretation and enforcement of the
provisions of this Agreement and in respect of the transactions contemplated
hereby and hereby waive, and agree not to assert, as a defense in any action,
suit or proceeding for the interpretation or enforcement hereof, that it is not
subject thereto or that such action, suit or proceeding may not be brought or is
not maintainable in said courts or that the venue


                                       13
<PAGE>



thereof may not be appropriate or that this Agreement may not be enforced in or
by such courts, and the parties irrevocably agree that all claims with respect
to such action or proceeding shall be heard and determined in such a court. The
parties hereby consent to and grant any such court jurisdiction over the person
of such parties and over the subject matter of such dispute and agree that
mailing of process or other papers in connection with any such action or
proceeding in the manner provided in Section 15, or in such other manner as may
be permitted by Law, shall be valid and sufficient service thereof. EACH PARTY
ACKNOWLEDGES AND AGREES THAT ANY CONTROVERSY WHICH MAY ARISE UNDER THIS
AGREEMENT IS LIKELY TO INVOLVE COMPLICATED AND DIFFICULT ISSUES, AND THEREFORE
EACH SUCH PARTY HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES ANY RIGHT SUCH
PARTY MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION DIRECTLY OR
INDIRECTLY ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE TRANSACTIONS
CONTEMPLATED BY THIS AGREEMENT. EACH PARTY CERTIFIES AND ACKNOWLEDGES THAT (i)
NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY OTHER PARTY HAS REPRESENTED,
EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF
LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER, (ii) EACH SUCH PARTY
UNDERSTANDS AND HAS CONSIDERED THE IMPLICATIONS OF THIS WAIVER, (iii) EACH SUCH
PARTY MAKES THIS WAIVER VOLUNTARILY, AND (iv) EACH SUCH PARTY HAS BEEN INDUCED
TO ENTER INTO THIS AGREEMENT BY, AMONG OTHER THINGS, THE MUTUAL WAIVERS AND
CERTIFICATIONS IN THIS SECTION 16.

         17. Expenses. Except as otherwise expressly provided herein or in the
Merger Agreement, all costs and expenses incurred in connection with this
Agreement and the transactions contemplated by this Agreement shall be paid by
the party incurring such expense, except that Issuer shall be responsible for
all fees and expenses (other than underwriting discounts or commissions)
relating to the registration of securities pursuant to Section 8.

         18. Entire Agreement, Etc. This Agreement, the Confidentiality
Agreement and the Merger Agreement (including any exhibits thereto, the BP Amoco
Disclosure Letter and the ARCO Disclosure Letter) constitute the entire
agreement, and supersede all other prior agreements, understandings,
representations and warranties, both written and oral, between the parties with
respect to the subject matter hereof. This Agreement shall inure to the benefit
of and be binding upon the parties hereto and their respective successors and
permitted assigns. This Agreement is not intended to confer upon any Person,
other than the parties


                                       14
<PAGE>



hereto, and their respective successors and permitted assigns, any rights or
remedies hereunder.

         19. Limitation on Profit. (a) Notwithstanding any other provision of
this Agreement, in no event shall Grantee's Total Profit (as hereinafter
defined) plus any ARCO Termination Amount paid to Grantee pursuant to Section
5.5.2 of the Merger Agreement exceed in the aggregate $500,000,000 (the "Maximum
Amount") and, if it otherwise would exceed such amount, Grantee, at its sole
election, shall either (i) reduce the number of Option Shares subject to this
Option, (ii) deliver to the Issuer for cancellation Option Shares previously
purchased by Grantee, (iii) pay cash to the Issuer, or (iv) any combination
thereof, so that Grantee's actually realized Total Profit, when aggregated with
such ARCO Termination Amount so paid to Grantee, shall not exceed the Maximum
Amount taking into account the foregoing actions.

         (b) Notwithstanding any other provision of this Agreement, this Option
may not be exercised for a number of Option Shares as would, as of the date of
exercise, result in a Notional Total Profit (as defined below) which, together
with any ARCO Termination Amount theretofore paid to Grantee pursuant to Section
5.5.2 of the Merger Agreement, and after giving effect to any election made by
Grantee under Section 19(a), would exceed the Maximum Amount; provided, that
nothing in this sentence shall restrict any exercise of the Option permitted
hereby on any subsequent date.

         (c) As used herein, the term "Total Profit" shall mean the aggregate
amount (before taxes) of the following: (i) the amount received by Grantee
pursuant to Issuer's repurchase of the Option or any Option Shares pursuant to
Section 9, less, in the case of any repurchase of Option Shares, Grantee's
purchase price for such Option Shares, and (ii) (x) the fair market value, or
the aggregate net cash amounts received by Grantee pursuant to the sale, of
Option Shares (or (A) any other securities into which such Option Shares are
converted or exchanged or (B) any property, cash or other securities received
pursuant to adjustments made under Section 7 ("Additional Property")), less (y)
Grantee's purchase price for such Option Shares.

            (d) As used herein, the term "Notional Total Profit" with respect to
the Option Shares subject to this Option shall be the Total Profit determined as
of the date of such proposal assuming that this Option were exercised in


                                       15
<PAGE>



full on such date and assuming that (i) such Option Shares (or any other
securities into which such Option Shares are converted or exchanged) were sold
for cash at the closing market price on the NYSE for the Common Stock as of the
close of business on the preceding trading day (less customary brokerage
commissions) and (ii) any Additional Property was sold at fair market value.

         20. Captions. The Section and paragraph captions herein are for
convenience of reference only, do not constitute part of this Agreement and
shall not be deemed to limit or otherwise affect any of the provisions hereof.


                                       16
<PAGE>


         IN WITNESS WHEREOF, this Agreement has been duly executed and delivered
by duly authorized officers of the parties hereto as of the day and year first
hereinabove written.


                            ATLANTIC RICHFIELD COMPANY



                            By: /s/ Mike R. Bowlin                      
                                ----------------------------------------
                                Name:  Mike R. Bowlin
                                Title: Chairman of the Board and
                                       Chief Executive Officer



                            BP AMOCO p.l.c.



                            By: /s/ John Browne                         
                                ----------------------------------------
                                Name:  (E.J.P. Browne) - Sir John Browne
                                Title: Chief Executive Officer



                            By: /s/ B.E. Grote                         
                                ----------------------------------------
                                Name:  B.E. Grote
                                Title: Executive Vice President


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