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* WHITE MOUNTAINS INSURANCE GROUP LTD (Last) (First) (Middle) 80 SOUTH MAIN STREET (Street) HANOVER NH 03755 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol MONTPELIER RE HOLDINGS LTD [ MRH ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 03/12/2004
	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	03/12/2004		S		4,500,000	D	$34.5	3,600,000	I	By OneBeacon Insurance Company(1)
Common Shares								900,000	I	By The Camden Fire Insurance Association(1)
Common Shares								1,800,000	I	By Pennsylvania General Insurance Company(1)

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
Warrant Shares	$16.67(2)							(3)	01/03/2012	Common Shares	7,172,357.5		7,172,357.5	I	By Fund American Reinsurance Company, Ltd.(4)

Explanation of Responses:

1. OneBeacon Insurance Company, The Camden Fire Insurance Association, and Pennsylvania General Insurance Company are indirect wholly-owned subsidiaries of White Mountains Insurance Group, Ltd.

2. Warrants Shares are exercisable for Common Shares on a 1 for 1 basis at an exercise price of $16.67 per Warrant Share.

3. Currently exercisable.

4. Fund American Reinsurance Company, Ltd. is an indirect wholly-owned subsidiary of White Mountains Insurance Group, Ltd.

Remarks:

	Dennis Beaulieu, Corporate Secretary, White Mountains Insurance Group, Ltd.	03/12/2004
	Dennis Beaulieu, by Power of Attorney on behalf of The Camden Fire Insurance Association, OneBeacon Insurance Company, and Pennsylvania General Insurance Company	03/10/2004
	Dennis Beaulieu, by Power of Attorney on behalf of Fund American Reinsurance Company, Ltd.	03/10/2004
	** 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).
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