UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

AMENDMENT NO. 3

TO

SCHEDULE TO

Tender Offer Statement under Section 14(d)(1) or 13(e)(1)
of the Securities Exchange Act of 1934

WHITE MOUNTAINS INSURANCE GROUP, LTD.

(Name of Subject Company (Issuer) and Filing Person (Issuer and Offeror))

Common Shares, par value $1.00 per share
(Title of Class of Securities)

G9618E107
(CUSIP Number of Class of Securities)

Robert L. Seelig, Esq.
Executive Vice President and General Counsel
White Mountains Insurance Group, Ltd.
80 South Main Street
Hanover, New Hampshire 03755-2053
Telephone: (603) 640-2200

(Name, address and telephone number of person authorized to receive notices and communications on behalf of filing persons)

With a copy to:

Ting S. Chen, Esq.
Cravath, Swaine & Moore LLP
825 Eighth Avenue
New York, New York 10019
Telephone: (212) 474-1000

CALCULATION OF FILING FEE:

*           This valuation represents the purchase of a total of 575,068 outstanding Common Shares, par value $1.00 per share, of White Mountains Insurance Group, Ltd. at the price of $875 per share.

**    The amount of the filing fee, calculated in accordance with Rule 0-11 of the Securities Exchange Act of 1934, as amended, equals $124.50 per million of the value of the transaction.

x  Check the box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

o    Check the box if the filing relates solely to preliminary communications made before the commencement of the tender offer.

Check the appropriate boxes below to designate any transactions to which the statement relates:

Check the following box if the filing is a final amendment reporting the results of the tender offer: x

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

INTRODUCTION

This Amendment No. 3 (this “Amendment”) amends and supplements the Issuer Tender Offer Statement on Schedule TO, initially filed by White Mountains Insurance Group, Ltd., a company organized under the laws of Bermuda (the “Company”), with the Securities and Exchange Commission on April 10, 2018 (as amended as of May 2, 2018, as of May 8, 2018 and as of the date hereof, the “Schedule TO”), which relates to the offer by the Company to purchase 500,000 of its issued and outstanding Common Shares, par value $1.00 per share (the “Common Shares” or the “Shares”), or such lesser number of Shares as is properly tendered and not properly withdrawn, at a price not greater than $875 or less than $825 per Share, net to the seller in cash, less any applicable withholding taxes and without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated April 10, 2018 (as amended as of May 2, 2018, the “Offer to Purchase”), and in the related Letter of Transmittal.

This Amendment is being filed in satisfaction of the reporting requirements of Rule 13e–4(c)(4) promulgated under the Securities Exchange Act of 1934, as amended. Except as otherwise set forth below, the information set forth in the Schedule TO, including all exhibits thereto that were previously filed with the Schedule TO, remains unchanged and is incorporated by reference as relevant to the items in this Amendment.

Item 11. Additional Information.

Item 11 of the Schedule TO is hereby amended and supplemented by adding the following to the end thereof:

On May 11, 2018, the Company issued a press release announcing the final results of the Offer. A copy of the press release is attached hereto as Exhibit (a)(5)(C) and incorporated herein by reference.

Item 12. Exhibits.

Item 12 of the Schedule TO is hereby amended and supplemented to add the following document filed herewith:

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SIGNATURE

After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

May 11, 2018

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INDEX OF EXHIBITS

*                                         Previously filed as exhibits to the Schedule TO.

**                                  Filed herewith.

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Exhibit (a)(5)(C)

PRESS RELEASE

WHITE MOUNTAINS ANNOUNCES
FINAL RESULTS OF ITS TENDER OFFER

HAMILTON, Bermuda, May 11, 2018 — White Mountains Insurance Group, Ltd. (NYSE: WTM) announced today the final results of its “modified Dutch auction” tender offer. The tender offer expired at 12:00 midnight, New York City time, at the end of the day on May 7, 2018.

Based on the final count by the depositary for the tender offer, 584,106 shares were properly tendered and not properly withdrawn at or below the final purchase price of $875 per share.

The tender offer was oversubscribed. Pursuant to the terms of the tender offer, the Company has purchased 575,068 shares at the final purchase price of $875 per share on a pro rata basis, except for tenders of odd lots, which have been accepted in full, for a total cost of approximately $503.2 million, excluding fees and expenses related to the tender offer. White Mountains has determined that the proration factor for the tender offer, after giving effect to the priority of the odd lots, is approximately 98.4%. The shares purchased in the tender offer represent approximately 15.3% of White Mountains’s shares outstanding as of April 9, 2018.

Payment for the shares purchased under the tender offer will be made promptly, and all shares tendered and not purchased will be returned promptly to shareholders.

The Company expects to have 3,178,337 common shares outstanding as of the time immediately following payment for the accepted shares.

Shareholders who have questions or would like additional information about the tender offer may contact the information agent for the tender offer, D.F. King & Co., at (800) 893-5865 (toll free) or by email at wtm@dfking.com. The dealer managers for the tender offer were J.P. Morgan Securities LLC and Barclays Capital Inc.

White Mountains is traded on the New York Stock Exchange under the symbol “WTM” and the Bermuda Stock Exchange under the symbol “WTM-BH”.

FORWARD-LOOKING STATEMENTS

This press release may contain “forward-looking statements”. All statements, other than statements of historical facts, included or referenced in this press release which address activities, events or developments which White Mountains expects or anticipates will or may occur in the future are forward-looking statements. The words “will”, “believe”, “intend”, “expect”, “anticipate”, “project”, “estimate”, “predict” and similar expressions are also intended to identify forward-looking statements. These forward-looking statements include, among others, statements with respect to White Mountains’s:

·                                  change in adjusted book value per share or return on equity;

·                                  business strategy;

·                                  financial and operating targets or plans;

·                                  incurred loss and loss adjustment expenses and the adequacy of its loss and loss adjustment expense reserves;

·                                  projections of revenues, income (or loss), earnings (or loss) per share, dividends, market share or other financial forecasts;

·                                  expansion and growth of its business and operations; and

·                                  future capital expenditures.

These statements are based on certain assumptions and analyses made by White Mountains in light of its experience and perception of historical trends, current conditions and expected future developments, as well as other factors believed to be appropriate in the circumstances. However, whether actual results and developments will conform to its expectations and predictions is subject to a number of risks and uncertainties that could cause actual results to differ materially from expectations, including:

·                                  the risks that are described from time to time in White Mountains’s filings with the Securities and Exchange Commission, including but not limited to White Mountains’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 filed February 28, 2018;

·                                  business opportunities (or lack thereof) that may be presented to it and pursued;

·                                  actions taken by ratings agencies from time to time, such as financial strength or credit ratings downgrades or placing ratings on negative watch;

·                                  the continued availability of capital and financing;

·                                  general economic, market or business conditions;

·                                  competitive forces, including the conduct of other insurers;

·                                  changes in domestic or foreign laws or regulations, or their interpretation, applicable to White Mountains, its competitors or its customers;

·                                  an economic downturn or other economic conditions adversely affecting its financial position; and

·                                  other factors, most of which are beyond White Mountains’s control.

Consequently, all of the forward-looking statements made in this press release are qualified by these cautionary statements, and there can be no assurance that the actual results or developments anticipated by White Mountains will be realized or, even if substantially realized, that they will have the expected consequences to, or effects on, White Mountains or its business or operations. Except for our obligations under Rule 13e-4(c)(3) and Rule 13e-4(e)(3) of the Exchange Act to disclose any material changes in the information previously disclosed to shareholders or as otherwise required by law, the Company assumes

no obligation to publicly update any such forward-looking statements, whether as a result of new information, future events or otherwise.