Third Party Reinsurance (Tables)

6 Months Ended

Jun. 30, 2011

Third Party Reinsurance

Listing of OneBeacon's top reinsurers

Top Reinsurers (Millions)	Balance at June 30, 2011		% of Total		A.M. Best Rating(1)
National Indemnity Company and General Reinsurance Corporation (2)	$	1,491.4	74	%	A++
Hanover Insurance Company	113.6		6	%	A
Tokio Marine and Nichido Fire (3)	64.2		3	%	A++
Tower Insurance Company	62.3		3	%	A-
Munich Reinsurance America	32.5		2	%	A+

(1) A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of fifteen ratings), “A+” (Superior, which is the second highest of fifteen ratings), “A” (Excellent, which is the third highest of fifteen ratings), and “A-” (Excellent, which is the fourth highest of fifteen ratings).

(2) Includes $193.5 of Third Party Recoverables (as defined below), which NICO (as defined below) would pay under the terms of the NICO Cover (as defined below) if they are unable to collect from third party reinsurers.

(3) Includes $37.1 of reinsurance recoverables from various third party reinsurers that are guaranteed by Tokio Marine and Nichido Fire under the terms of a 100% quota share reinsurance agreement between Houston General Insurance Company and Tokio Marine and Nichido Fire.

Listing of White Mountains Re's top reinsurers

Top Reinsurers (Millions)	Balance at June 30, 2011		% of Total		A.M. Best Rating (1)	% Collateralized
Olympus (2)	$	44.8	11	%	NR-5	100	%
Lloyds of London(3)	43.7		11	%	A	3	%
General Reinsurance Corporation	43.3		11	%	A++	2	%
Swiss Re Group	39.5		10	%	A	4	%
Michigan Catastrophic Claims Association	15.2		4	%	N/A(4)	—	%

(1) A.M. Best ratings as detailed above are: “NR-5” (Not formally followed), “A++” (Superior, which is the highest of fifteen ratings), and “A” (Excellent, which is the third highest of fifteen ratings).

(2) Non-U.S. insurance entity. Balances are fully collateralized through funds held, letters of credit or trust agreements.

(3) Represents the total of reinsurance recoverables due to White Mountains Re from all Lloyds Syndicates.

(4) Michigan Catastrophic Claims Association (“MCCA”) is a non-profit unincorporated association of which every insurance company that sells automobile coverage in Michigan is required to be a member.  A.M. Best does not rate MCCA.  White Mountains Re acquired its recoverable from MCCA pursuant to its acquisition of Stockbridge.