WASHINGTON, D.C. 20549

                                    FORM 13F

                               FORM 13F COVER PAGE

Report for the Calendar Year or Quarter Ended: December 31, 2008

Check Here if Amendment / /; Amendment Number:
   This Amendment (Check only one.):    / / is a restatement.
                                        / / adds new holdings entries.

Institutional Investment Manager Filing this Report:

   Name:         White Mountains Insurance Group, Ltd.
   Address:      80 South Main Street
                 Hanover, New Hampshire  03755-2053

Form 13F File Number: 028-01681

The institutional investment manager filing this report and the person by whom
it is signed hereby represent that the person signing the report is authorized
to submit it, that all information contained herein is true, correct and
complete, and that it is understood that all required items, statements,
schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:

Name:    J. Brian Palmer
Title:   Chief Accounting Officer
Phone:   (603) 640-2200

Signature, Place, and Date of Signing:

       /s/ J. Brian Palmer           Boston, Massachusetts   February 13, 2009
   -------------------------------   ---------------------   -----------------
           [Signature]                   [City, State]            [Date]

Report Type (Check only one.):

/ / 13F HOLDINGS REPORT. (Check here if all holdings of this reporting
    manager are reported in this report.)

/X/ 13F NOTICE. (Check here if no holdings reported are in this report,
    and all holdings are reported by other reporting manager(s).)

/ / 13F COMBINATION REPORT. (Check here if a portion of the holdings for this
    reporting manager are reported in this report and a portion are reported by
    other reporting manager(s).)

List of Other Managers Reporting for this Manager:

No.       Form 13F File Number         Name

1.             028-00470               White Mountains Advisors LLC