Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 333-132388) of White Mountains Insurance Group Ltd. of our report dated June 26, 2008 with respect to the statements of net assets available for benefits of Esurance Inc. 401(k) Plan as of December 31, 2007 and 2006, the related statements of changes in net assets available for benefits for the years then ended, and the related supplemental Schedule H, Line 4i -Schedule of Assets (Held at End of Year) as of December 31, 2007, which report appears in the December 31, 2007 annual report on Form 11-K of Esurance Inc. 401(k) Plan.

/s/ Mohler, Nixon & Williams

MOHLER, NIXON & WILLIAMS

Accountancy Corporation

Campbell, California

June 26, 2008