SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* BYRNE JOHN JOSEPH (Last) (First) (Middle) C/O WHITE MOUNTAINS INSURANCE GROUP, LTD 80 SOUTH MAIN STREET (Street) HANOVER NH 03755 (City) (State) (Zip)	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)
	3. Date of Earliest Transaction (Month/Day/Year) 03/07/2005
	4. If Amendment, Date of 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

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)

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 Securities Underlying Derivative Security (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: 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

Explanation of Responses:

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.

Remarks:

	John J. Byrne	03/09/2005
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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