Know all by these presents, that the undersigned hereby
constitutes and appoints each of Robert L. Seelig, General
Counsel, and Jennifer L. Pitts, Secretary, of White
Mountains Insurance Group, Ltd. (WTM), and Jason R. Lichtenstein,
Vice President & Associate General Counsel of White Mountains
Capital, Inc., signing singly, the undersigned's true and
lawful attorney-in-fact to: (1) execute for and on behalf
of the undersigned, in the undersigned's capacity as a
legal entity, Forms 3, 4, and 5 in accordance with Section
16(a) of the Securities Exchange Act of 1934 and the rules
thereunder; (2) do and perform any and all acts for and on
behalf of the undersigned which may be necessary or desirable
to complete and execute any such Form 3, 4, or 5, complete
and execute any amendment or amendments thereto, and timely
file such form with the United States Securities and Exchange
Commission and any stock exchange or similar authority; and
(3) take any other action of any type whatsoever in connection
with the foregoing which, in the opinion of such attorney-in-fact,
may be of benefit to, in the best interest of, or legally
required by, the undersigned, it being understood that the
documents executed by such attorney-in-fact on behalf of the
undersigned pursuant to this Power of Attorney shall be in
such form and shall contain such terms and conditions as such
attorney-in-fact may approve in such attorney-in-fact's discretion.
The undersigned hereby grants to each such attorney-in-fact full
power and authority to do and perform any and every act and thing
whatsoever requisite, necessary, or proper to be done in the
exercise of any of the rights and powers herein granted, as
fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or
revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or
substitutes, shall lawfully do or cause to be done by virtue of
this power of attorney and the rights and powers herein granted.
The undersigned acknowledges that the foregoing attorneys-in-fact,
in serving in such capacity at the request of the undersigned,
are not rendering legal advice of any form, other than
satisfying regulatory filing requirements, with respect to
any transactions to be reported on Forms 3, 4 and 5 are not
assuming any of the undersigned's responsibilities to comply
with Section 16 of the Securities Exchange Act of 1934.
The undersigned hereby grants this Power of Attorney with the
understanding that information provided to each such
attorney-in-fact is strictly confidential and will not be
disclosed to senior management, directors or other third parties
whether affiliated or otherwise and will be used solely to
complete and execute any such Form 3, 4 or 5, complete and
execute any amendment or amendments thereto, and timely file
such form with the United States Securities and Exchange
Commission and any stock exchange or similar authority.
This Power of Attorney shall remain in full force and effect
until the undersigned is no longer required to file Forms 3,
4, and 5 with respect to the undersigned's, or any affiliate
of WTM, holdings of and transactions in publicly-traded
securities, unless earlier revoked by the undersigned in
a signed writing delivered to the foregoing attorneys-in-fact.
IN WITNESS WHEREOF, the undersigned has caused this Power
of Attorney to be executed as of
this 2nd day of April 2012.


/s/ John J. Byrne