Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
BYRNE JOHN JOSEPH
   2. Issuer Name and Ticker or Trading Symbol
WHITE MOUNTAINS INSURANCE GROUP LTD [WTM] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
C/O WHITE MOUNTAINS INSURANCE GROUP, LTD, 80 SOUTH MAIN STREET		 3. Date of Earliest Transaction (Month/Day/Year)
03/07/2005
(Street)

HANOVER, NH 03755		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Shares 02/17/2005   G V 496 D (1) 416,834 D  
Common Shares 03/07/2005   S   400 D $ 675 416,434 D  
Common Shares 03/07/2005   S   1,500 D $ 676 414,934 D  
Common Shares 03/07/2005   S   100 D $ 674 414,834 D  
Common Shares 03/07/2005   S   200 D $ 673.5 414,634 D  
Common Shares 03/07/2005   S   300 D $ 673 414,334 D  
Common Shares 03/07/2005   S   200 D $ 671.5 414,134 D  
Common Shares 03/07/2005   S   100 D $ 671.01 414,034 D  
Common Shares 03/07/2005   S   300 D $ 671 413,734 D  
Common Shares 03/07/2005   S   100 D $ 670 413,634 D  
Common Shares 03/07/2005   S   1,100 D $ 668 412,534 D  
Common Shares 03/07/2005   S   100 D $ 667.9 412,434 D  
Common Shares 03/07/2005   S   400 D $ 667 412,034 D  
Common Shares 03/07/2005   S   100 D $ 666.01 411,934 D  
Common Shares 03/07/2005   S   100 D $ 666 411,834 D  
Common Shares               614,700 (2) I By Family Trusts (GRAT)
Common Shares               50 I By wife
Common Shares               2 I By 401(k)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
BYRNE JOHN JOSEPH
C/O WHITE MOUNTAINS INSURANCE GROUP, LTD
80 SOUTH MAIN STREET
HANOVER, NH 03755		   X      

Signatures

 John J. Byrne   03/09/2005
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Value of WTM Common Shares gifted based on the closing price of WTM Common Shares on February 16, 2005.
(2) Since February 4, 2005, the Reporting Person's last report, 9,372 WTM Common Shares previously held in a grantor retained annuity trust have been transferred and are now owned directly.

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