UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 11-K (Mark One) |X| Annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2001 OR |_| Transition report pursuant to Section 15(d) of the Securities Exchange Act of 1934 For the transition period from ___________ to ___________ Commission file number 1-8993 A. Full title of the plan and the address of the plan, if different from that of the issuer named below: ONEBEACON INSURANCE SAVINGS PLAN One Beacon Street Boston, Massachusetts 02108 B. Name of issuer of the securities held pursuant to the plan and the address of its principal executive office: WHITE MOUNTAINS INSURANCE GROUP, LTD. 28 Gates Street White River Junction, Vermont 05001-7066 (802) 295-4500 EXPLANATORY NOTE This Annual Report on Form 11-K is being filed so that it may be incorporated by reference into a Registration Statement on Form S-8 which White Mountains Insurance Group, Ltd. is filing with respect Common Shares, $1.00 par value per share, of White Mountains Insurance Group, Ltd. issuable under the Plan. INFORMATION FILED The following financial statements and exhibit are filed with, and included in, this Report: A. Financial statements for the Plan consisting of: 1. Report of Independent Accountants; 2. Statements of Net Assets Available for Plan Benefits as of December 31, 2001 and 2000; 3. Statements of Changes in Net Assets Available for Plan Benefits for the years ended December 31, 2001 and 2000; 4. Notes to Financial Statements; 5. Schedule of Assets Held at End of Year as of December 31, 2001; and B. Consent of Independent Accountants SIGNATURES THE PLAN. Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed on its behalf by the undersigned, thereunto duly authorized. ONEBEACON INSURANCE SAVINGS PLAN (the "Plan") Date: June 26, 2002 By: /s/ JAMES J. RITCHIE ------------------------------------ Title: Chief Financial Officer of One Beacon Insurance Company (the Plan Administrator) and Member of the Benefits Committee EXHIBIT INDEX EXHIBIT NUMBER DESCRIPTION -------------- ----------- (A) Financial statements for the Plan consisting of: 1. Report of Independent Accountants; 2. Statement of Net Assets Available For Plan Benefits as of December 31, 2001 and 2000; 3. Statement of Changes in Net Assets Available for Plan Benefits for the years ended December 31, 2001 and 2000; 4. Notes to Financial Statements; 5. Schedule of Assets Held at End of Year as of December 31, 2001; and (B) Consent of Independent Accountants