<PAGE>
EXHIBIT (a)(1)(c)
WHITE MOUNTAINS INSURANCE GROUP, LTD.
FORM OF NOTICE OF GUARANTEED DELIVERY
This form, or a form substantially equivalent to this form, must be
used to accept the Offer (as defined below) if a shareholder's share
certificates are not immediately available, if the procedure for book-entry
transfer cannot be completed on a timely basis, or if time will not permit the
Letter of Transmittal or other required documents to reach the Depositary prior
to the Expiration Date (as defined in the Offer). Such form may be delivered to
the Depositary by hand, mail, telex or (for Eligible Institutions only) by
facsimile transmission. See Section 3 of the Offer to Purchase.
THE ELIGIBLE INSTITUTION WHICH COMPLETES THIS FORM MUST COMMUNICATE THE
GUARANTEE TO THE DEPOSITARY AND MUST DELIVER THE LETTER OF TRANSMITTAL AND
CERTIFICATES FOR SHARES TO THE DEPOSITARY WITHIN THE TIME SHOWN HEREIN. FAILURE
TO DO SO COULD RESULT IN FINANCIAL LOSS TO SUCH ELIGIBLE INSTITUTION.
THE DEPOSITARY
EQUISERVE TRUST COMPANY
FACSIMILE TRANSMISSION:
(FOR ELIGIBLE INSTITUTIONS ONLY)
(781) 575-4826
or
(781) 575-4827
FOR CONFIRMATION CALL:
(781) 575-4816
BY FEDERAL EXPRESS OR OTHER COURIER:
BY MAIL: Equiserve BY HAND:
Equiserve 40 Campanelli Drive Equiserve
P.O. Box 842010 Braintree, MA 02184 c/o Securities Transfer
Boston, MA 02284-2010 Attn: White Mountains and Reporting Services Inc.
Attn: Corporate Actions
100 William Street, Galleria
New York, NY 10038
DELIVERY OF THIS INSTRUMENT TO AN ADDRESS OTHER THAN AS SET
FORTH ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE
NUMBER OTHER THAN THE ONE LISTED ABOVE WILL NOT
CONSTITUTE A VALID DELIVERY.
FOR INFORMATION CALL THE INFORMATION AGENT:
EQUISERVE TRUST COMPANY
1-888-756-1854
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Ladies and Gentlemen:
The undersigned hereby tenders to White Mountains Insurance Group, Ltd.
(the "Company"), upon the terms and subject to the conditions set forth in its
Offer to Purchase dated August 21, 2000, and the related Letter of Transmittal
(which together constitute the "Offer"), receipt of which is hereby
acknowledged, the number of Common Shares of the Company, par value $1.00 per
share ("Shares"), listed below, pursuant to the guaranteed delivery procedures
set forth in Section 3 of the Offer to Purchase.
NUMBER OF SHARES: SIGN HERE:
-------------------------------------- ---------------------------------
Certificate Nos: (if available) Name(s) (Please Print)
-------------------------------------- ---------------------------------
-------------------------------------- ---------------------------------
(Area Code and Telephone Number) (Address)
Account No. ___________________________ _________________________________
(At the Depository Trust Company) Signature(s)
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ODD LOTS
(SEE INSTRUCTION 7 OF THE LETTER OF TRANSMITTAL)
TO BE COMPLETED ONLY IF SHARES ARE BEING TENDERED BY OR ON BEHALF OF A
PERSON WHO BENEFICIALLY OWNED AS OF THE CLOSE OF BUSINESS ON AUGUST 14, 2000,
AND WHO WILL CONTINUE TO OWN BENEFICIALLY UNTIL THE EXPIRATION DATE AN AGGREGATE
OF FEWER THAN 100 SHARES.
THE UNDERSIGNED EITHER (CHECK ONE BOX):
/ / WAS THE BENEFICIAL OWNER AS OF THE CLOSE OF BUSINESS ON AUGUST 14,
2000, AND WILL CONTINUE TO BE THE BENEFICIAL OWNER UNTIL THE EXPIRATION
DATE OF AN AGGREGATE OF FEWER THAN 100 SHARES, AND IS TENDERING ALL
SUCH SHARES, OR
/ / IS AN "ELIGIBLE INSTITUTION" THAT (I) IS TENDERING, FOR THE
BENEFICIAL OWNERS THEREOF, SHARES WITH RESPECT TO WHICH IT IS THE
RECORD OWNER, AND (II) BELIEVES, BASED UPON REPRESENTATIONS MADE TO IT
BY EACH SUCH BENEFICIAL OWNER, THAT EACH SUCH BENEFICIAL OWNER
BENEFICIALLY OWNED AS OF THE CLOSE OF BUSINESS ON AUGUST 14, 2000, AND
WILL CONTINUE TO OWN BENEFICIALLY UNTIL THE EXPIRATION DATE AN
AGGREGATE OF FEWER THAN 100 SHARES, AND IS TENDERING ALL SUCH SHARES.
______________________________________________________________________________
_______________________________________ ___________________________
No. of Shares tendered SIGN HERE
_______________________________________ ____________________________
Certificate Nos. (if available): (Signature(s))
_______________________________________ ____________________________
If Shares will be delivered by (Signature(s))
book-entry transfer:
Name of Tendering Institution:_________ _____________________________
_______________________________________ (Name(s)) (Please Print)
Account No. at The Depository ____________________________
Trust Company__________________________ (Address)
_______________________________________ ____________________________
(Zip Code)
____________________________
(Area Code and Telephone No.)
______________________________________ ____________________________
GUARANTEE
(Not to be used for signature guarantee)
THE UNDERSIGNED, A FINANCIAL INSTITUTION THAT IS A PARTICIPANT IN THE
SECURITIES TRANSFER AGENTS MEDALLION SIGNATURE GUARANTEE PROGRAM OR THE NEW YORK
STOCK MEDALLION SIGNATURE PROGRAM OR THE STOCK EXCHANGES MEDALLION PROGRAM,
HEREBY GUARANTEES (i) THAT THE ABOVE-NAMED PERSON(S) HAS A NET LONG POSITION IN
THE SHARES BEING TENDERED WITHIN THE MEANING OF RULE 14e-4 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED, (ii) THAT SUCH TENDER OF SHARES
COMPLIES WITH RULE 14e-4, AND (iii) TO DELIVER TO THE DEPOSITARY AT ONE OF ITS
ADDRESSES SET FORTH ABOVE CERTIFICATE(S) FOR THE SHARES TENDERED HEREBY, IN
PROPER FORM FOR TRANSFER, OR A CONFIRMATION OF THE BOOK-ENTRY TRANSFER OF THE
SHARES INTO THE DEPOSITARY'S ACCOUNT AT THE DEPOSITORY TRUST COMPANY, TOGETHER
WITH A PROPERLY COMPLETED AND DULY EXECUTED LETTER OF TRANSMITTAL (OR FACSIMILE
THEREOF) AND ANY OTHER REQUIRED DOCUMENTS, WITHIN THREE NEW YORK STOCK EXCHANGE
TRADING DAYS AFTER THE DATE OF RECEIPT BY THE DEPOSITARY.
________________________________________________________________________________
Name of Firm: Address:
_________________________________ ________________________________
(Authorized Signature) (Zip Code)
Area Code and
Name:____________________________ Telephone No.:__________________
(Please Print)
Title:___________________________ Dated:_____________________________________
________________________________________________________________________________
THIS FORM IS NOT TO BE USED TO GUARANTEE SIGNATURES. IF A SIGNATURE ON A LETTER
OF TRANSMITTAL IS REQUIRED TO BE GUARANTEED BY AN ELIGIBLE INSTITUTION UNDER THE
INSTRUCTIONS THERETO, SUCH SIGNATURE GUARANTEE MUST APPEAR IN THE APPLICABLE
SPACE PROVIDED IN THE SIGNATURE BOX ON THE LETTER OF TRANSMITTAL.
DO NOT SEND SHARE CERTIFICATES WITH THIS FORM. YOUR SHARE CERTIFICATES MUST BE
SENT WITH THE LETTER OF TRANSMITTAL
_________________________________ _____________________________________
_________________________________ _____________________________________
