UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   FORM 13F

                              FORM 13F COVER PAGE

  INFORMATION REQUIRED OF INSTITUTIONAL INVESTMENT MANAGERS PURSUANT
TO SECTION 13(f) OF THE SECURITIES EXCHANGE ACT OF 1934 AND RULES THEREUNDER

Report for the Calendar Year or Quarter Ended: March 31, 2004
                                               -----------------------

Check Here if Amendment / /; Amendment Number:
                                               ---------
   This Amendment (Check only one.):    / / is a restatement.
                                        / / adds new holdings entries.

Institutional Investment Manager Filing this Report:

   Name:         White Mountains Insurance Group, Ltd.
   Address:      80 South Main Street
                 Hanover, New Hampshire 03755
                 USA

Form 13F File Number: 028-01681

The institutional investment manager filing this report and the person by
whom it is signed hereby represent that the person signing the report is
authorized to submit it, that all information contained herein is true,
correct and complete, and that it is understood that all required items,
statements, schedules, lists, and tables, are considered integral parts of
this form.

Person Signing this Report on Behalf of Reporting Manager:

Name:    J. Brian Palmer
Title:   Chief Accounting Officer
Phone:   (603) 640-2200

Signature, Place, and Date of Signing:

     /s/ J. Brian Palmer           Hanover, New Hampshire     May 14, 2004
 -------------------------------   -----------------------    ------------
         [Signature]                   [City, State]            [Date]

Report Type (Check only one.):

/X/ 13F HOLDINGS REPORT. (Check here if all holdings of this reporting
    manager are reported in this report.)

/ / 13F NOTICE. (Check here if no holdings reported are in this report,
    and all holdings are reported by other reporting manager(s).)

/ / 13F COMBINATION REPORT. (Check here if a portion of the holdings for this
    reporting manager are reported in this report and a portion are reported by
    other reporting manager(s).)



                             FORM 13F SUMMARY PAGE

Report Summary:


Number of Other Included Managers:                2
                                        --------------------

Form 13F Information Table Entry Total:      113 items
                                        --------------------

Form 13F Information Table Value Total:    $907,649,773
                                        --------------------


List of Other Included Managers:

Provide a numbered list of the name(s) and Form 13F file number(s) of all
institutional investment managers with respect to which this report is filed,
other than the manager filing this report.

    No.       Form 13F File Number         Name

    1.        028-07388                 Folksamerica Holding Company, Inc.
    2.        028-00470                 White Mountains Advisors LLC




                  WHITE MOUNTAINS INSURANCE GROUP, LTD.

                       WHITE MOUNTAINS ADIVSORS
                FORM 13F INFORMATION TABLE--MARCH 31, 2004

CUSIP MARKET AMOUNT AND INVESTMENT VOTING AUTHORITY(SHARES) NAME OF ISSUER TITLE OF CLASS NUMBER VALUE TYPE OF SECURITY DISCRETION MANAGERS* SOLE SHARED NONE - ------------------------- ---------------- --------- ---------- ---------------- ---------- --------- ------ -------- ------ EVEREST RE GROUP LTD SHS G3223R108 508,368 5,950 DEFINED 1, 3 5,950 MONTPELIER RE HOLDINGS LTD. SHS G62185106 228,375,000 6,300,000 DEFINED 2, 3 6,300,000 ABITIBI-CONSOLIDATED INC COM 003924107 177,250 25,000 DEFINED 1, 3 25,000 ABITIBI-CONSOLIDATED INC COM 003924107 5,175,700 730,000 DEFINED 2, 3 730,000 AETNA INC COM 00817Y108 421,684 4,700 DEFINED 1, 3 4,700 ALLEGHENY ENERGY INC COM 017361106 263,232 19,200 DEFINED 1, 3 19,200 ALLEGHENY ENERGY INC COM 017361106 1,713,750 125,000 DEFINED 2, 3 125,000 AMERADA HESS CORP COM 023551104 3,727,488 57,100 DEFINED 1, 3 57,100 AMERADA HESS CORP COM 023551104 58,099,200 890,000 DEFINED 2, 3 890,000 AMERICAN INT'L. GROUP COM 026874107 642,150 9,000 DEFINED 2, 3 9,000 AON CORP COM 037389103 3,224,721 115,540 DEFINED 1, 3 115,540 AON CORP COM 037389103 9,489,400 340,000 DEFINED 2, 3 340,000 ARCHER DANIELS MIDLAND COM 039483102 759,150 45,000 DEFINED 1, 3 45,000 ARCHER DANIELS MIDLAND COM 039483102 12,399,450 735,000 DEFINED 2, 3 735,000 ASSURANT INC COM 04621X108 218,805 8,700 DEFINED 1, 3 8,700 AUTOMATIC DATA PROCESSING INC. COM 053015103 747,600 17,800 DEFINED 1, 3 17,800 AUTOMATIC DATA PROCESSING INC. COM 053015103 22,680,000 540,000 DEFINED 2, 3 540,000 BANK OF HAWAII CORP COM 062540109 609,240 13,150 DEFINED 1, 3 13,150 BANKNORTH GROUP COM 06646R107 680,800 20,000 DEFINED 2, 3 20,000 BENFIELD GROUP PLC COM 1011971*2 34,691,131 7,882,499 DEFINED 2, 3 7,882,499 BERKSHIRE HATHAWAY INC CL B 084670207 2,401,700 772 DEFINED 1, 3 772 BERKSHIRE HATHAWAY INC CL A 084670108 9,983,100 107 DEFINED 2, 3 107 BERKSHIRE HATHAWAY INC CL B 084670207 10,266,333 3,300 DEFINED 2, 3 3,300 BISYS GROUP INC COM 055472104 169,611 10,120 DEFINED 1, 3 10,120 CALLAWAY GOLF COMPANY COM 131193104 284,700 15,000 DEFINED 1, 3 15,000 CALLAWAY GOLF COMPANY COM 131193104 4,555,200 240,000 DEFINED 2, 3 240,000 CAPITOL FEDERAL FINANCIAL COM 14057C106 897,500 25,000 DEFINED 1, 3 25,000 CAPITOL FEDERAL FINANCIAL COM 14057C106 9,477,600 264,000 DEFINED 2, 3 264,000 CHARTER FINANCIAL CORP COM 16122M100 6,692,900 170,000 DEFINED 2, 3 170,000 CLOROX COMPANY COM 189054109 413,290 8,450 DEFINED 1, 3 8,450 COLGATE-PALMOLIVE CO COM 194162103 1,377,500 25,000 DEFINED 2, 3 25,000 COUNTRYWIDE CREDIT IND INC COM 222372104 1,086,835 11,333 DEFINED 1, 3 11,333 DELTIC TIMBER CORP COM 247850100 2,128,800 60,000 DEFINED 2, 3 60,000 DELUXE CORP COM 248019101 561,400 14,000 DEFINED 2, 3 14,000 DIAMOND OFFSHORE DRILLING INC COM 25271C102 362,850 15,000 DEFINED 1, 3 15,000 DIAMOND OFFSHORE DRILLING INC COM 25271C102 5,079,900 210,000 DEFINED 2, 3 210,000 EASTMAN CHEMICAL COM 277432100 1,067,000 25,000 DEFINED 1, 3 25,000 EASTMAN CHEMICAL COM 277432100 8,962,800 210,000 DEFINED 2, 3 210,000 EL PASO ELECTRIC CO COM 283677854 2,618,528 189,200 DEFINED 1, 3 189,200 EL PASO ELECTRIC CO COM 283677854 27,126,400 1,960,000 DEFINED 2, 3 1,960,000
CUSIP MARKET AMOUNT AND INVESTMENT VOTING AUTHORITY(SHARES) NAME OF ISSUER TITLE OF CLASS NUMBER VALUE TYPE OF SECURITY DISCRETION MANAGERS* SOLE SHARED NONE - ------------------------- ---------------- --------- ---------- ---------------- ---------- --------- ------ -------- ------ EQUITY OFFICE PROPERTIES TR COM 294741103 560,466 19,400 DEFINED 1, 3 19,400 ETHAN ALLEN COM 297602104 660,160 16,000 DEFINED 2, 3 16,000 FAIRMONT HOTELS & RESORTS COM 305204109 425,035 16,900 DEFINED 1, 3 16,900 FAIRMONT HOTELS & RESORTS COM 305204109 4,778,500 190,000 DEFINED 2, 3 190,000 FIRST DATA CORP COM 319963104 9,308,928 220,800 DEFINED 1, 3 220,800 FIRST ENERGY CORP COM 337932107 2,012,620 51,500 DEFINED 1, 3 51,500 FIRST ENERGY CORP COM 337932107 32,241,000 825,000 DEFINED 2, 3 825,000 FIRST HEALTH GROUP CORP COM 320960107 264,385 12,100 DEFINED 1, 3 12,100 FORTUNE BRANDS INC. COM 349631101 7,663,000 100,000 DEFINED 2, 3 100,000 GOLDMAN SACHS GROUP COM 38141G104 521,750 5,000 DEFINED 2, 3 5,000 GREAT LAKES CHEMICAL CORP COM 390568103 1,431,000 60,000 DEFINED 1, 3 60,000 GREAT LAKES CHEMICAL CORP COM 390568103 27,069,750 1,135,000 DEFINED 2, 3 1,135,000 HEALTH NET INC COM 42222G108 498,600 20,000 DEFINED 1, 3 20,000 HIBERNIA CORP CLASS A COM 428656102 418,122 17,800 DEFINED 1, 3 17,800 HONDA MOTOR CO COM 438128308 694,200 30,000 DEFINED 2, 3 30,000 HONEYWELL INC. COM 438516106 1,015,500 30,000 DEFINED 2, 3 30,000 IDACORP INC COM 451107106 2,093,000 70,000 DEFINED 2, 3 70,000 ILLINOIS TOOL WORKS COM 452308109 1,584,600 20,000 DEFINED 2, 3 20,000 INTL SPEEDWAY CORP COM 460335201 280,120 5,960 DEFINED 1, 3 5,960 JEFFERSON PILOT CORPORATION COM 475070108 1,650,300 30,000 DEFINED 2, 3 30,000 L-3 COMMUNICATIONS HOLDINGS I COM 502424104 1,189,600 20,000 DEFINED 2, 3 20,000 LAFARGE NORTH AMERICA INC COM 505862102 682,920 16,800 DEFINED 1, 3 16,800 LEUCADIA NATL CORP COM 527288104 1,762,875 33,087 DEFINED 1, 3 33,087 LEUCADIA NATL CORP COM 527288104 13,447,819 252,399 DEFINED 2, 3 252,399 LONGVIEW FIBRE CO COM 543213102 390,600 35,000 DEFINED 1, 3 35,000 LONGVIEW FIBRE CO COM 543213102 9,374,400 840,000 DEFINED 2, 3 840,000 MARATHON OIL CORP COM 565849106 2,976,428 88,400 DEFINED 1, 3 88,400 MARATHON OIL CORP COM 565849106 45,959,550 1,365,000 DEFINED 2, 3 1,365,000 MARSH & MCLENNAN COM 571748102 2,315,000 50,000 DEFINED 2, 3 50,000 MASCO CORPORATION COM 574599106 1,065,400 35,000 DEFINED 2, 3 35,000 MATTEL COM 577081102 1,659,600 90,000 DEFINED 2, 3 90,000 MCDONALDS CORP COM 580135101 628,540 22,000 DEFINED 1, 3 22,000 MCDONALDS CORP COM 580135101 10,999,450 385,000 DEFINED 2, 3 385,000 MELLON BK CORP COM 58551A108 625,800 20,000 DEFINED 2, 3 20,000 MERCK & CO. INC. COM 589331107 547,956 12,400 DEFINED 1, 3 12,400 MEREDETH CORP. COM 589433101 1,011,200 20,000 DEFINED 1, 3 20,000 MEREDETH CORP. COM 589433101 23,257,600 460,000 DEFINED 2, 3 460,000 NUI CORP COM 629431107 627,361 37,100 DEFINED 1, 3 37,100 NUI CORP COM 629431107 6,256,700 370,000 DEFINED 2, 3 370,000 OCTEL CORP COM 675727101 895,500 30,000 DEFINED 1, 3 30,000 OCTEL CORP COM 675727101 36,058,800 1,208,000 DEFINED 2, 3 1,208,000 OHIO CASUALTY CORP COM 677240103 541,729 27,100 DEFINED 1, 3 27,100 OVERSEAS SHIPPING GROUP COM 690368105 2,555,000 70,000 DEFINED 2, 3 70,000 PAULA FINANCIAL COM 703588103 234,000 65,000 DEFINED 2, 3 65,000 PEOPLES BANK COM 710198102 836,820 18,000 DEFINED 1, 3 18,000 PEOPLES BANK COM 710198102 14,411,900 310,000 DEFINED 2, 3 310,000 PEPSICO INCORPORATED COM 713448108 635,430 11,800 DEFINED 1, 3 11,800 PLUM CREEK TIMBER CO COM 729251108 812,000 25,000 DEFINED 2, 3 25,000
CUSIP MARKET AMOUNT AND INVESTMENT VOTING AUTHORITY(SHARES) NAME OF ISSUER TITLE OF CLASS NUMBER VALUE TYPE OF SECURITY DISCRETION MANAGERS* SOLE SHARED NONE - ------------------------- ---------------- --------- ---------- ---------------- ---------- --------- ------ -------- ------ POST PROPERTIES INC COM 737464107 397,440 13,800 DEFINED 1, 3 13,800 POTLATCH CORPORATION COM 737628107 815,000 20,000 DEFINED 1, 3 20,000 POTLATCH CORPORATION COM 737628107 18,337,500 450,000 DEFINED 2, 3 450,000 RYDER SYSTEM COM 783549108 1,161,900 30,000 DEFINED 1, 3 30,000 RYDER SYSTEM COM 783549108 22,269,750 575,000 DEFINED 2, 3 575,000 RYLAND GROUP INC COM 783764103 257,607 2,900 DEFINED 1, 3 2,900 SAFEWAY INC. COM 786514208 411,600 20,000 DEFINED 2, 3 20,000 SCHERING-PLOUGH COM 806605101 295,204 18,200 DEFINED 1, 3 18,200 SEMCO ENERGY INC COM 78412D109 311,300 55,000 DEFINED 2, 3 55,000 SIERRA PACIFIC RESOURCES COM 826428104 688,200 93,000 DEFINED 1, 3 93,000 SIERRA PACIFIC RESOURCES COM 826428104 6,290,000 850,000 DEFINED 2, 3 850,000 STANLEY WORKS COM 854616109 2,134,000 50,000 DEFINED 2, 3 50,000 TJX COMPANIES INC COM 872540109 1,473,600 60,000 DEFINED 2, 3 60,000 TORONTO-DOMINION BANK COM 891160509 351,500 10,000 DEFINED 2, 3 10,000 TXU CORP COM 873168108 2,292,800 80,000 DEFINED 2, 3 80,000 UICI COM 902737105 149,076 10,100 DEFINED 1, 3 10,100 UNIONBANCAL CORPORATION COM 908906100 1,267,838 24,200 DEFINED 1, 3 24,200 UNISOURCE ENERGY CORP. HLD. CO COM 909205106 3,515,967 143,100 DEFINED 1, 3 143,100 UNISOURCE ENERGY CORP. HLD. CO COM 909205106 40,786,200 1,660,000 DEFINED 2, 3 1,660,000 UNOCAL CORP COM 915289102 2,307,632 61,900 DEFINED 1, 3 61,900 UNOCAL CORP COM 915289102 29,078,400 780,000 DEFINED 2, 3 780,000 WACHOVIA CORP COM 929903102 643,430 13,690 DEFINED 1, 3 13,690 WELLPOINT HEALTH NETWORKS COM 94973H108 2,274,400 20,000 DEFINED 2, 3 20,000 XCEL ENERGY INC COM 98389B100 623,350 35,000 DEFINED 1, 3 35,000 XCEL ENERGY INC COM 98389B100 12,467,000 700,000 DEFINED 2, 3 700,000
1 = FolksAmerica Holding Company Inc. (Form 13F filed separately) 2 = White Mountains Advisors (Form 13F filed separately) 3 = White Mountains Insurance Group, Ltd.