Exhibit 10.23

                   ONEBEACON'S 2004 MANAGEMENT INCENTIVE PLAN

PURPOSE
The Management Incentive Plan (MIP) is an integral part of the total
compensation program for senior Home Office and Field Office management. Its
primary purpose is to focus attention on 2004 profitability goals and to reward
eligible participants for the achievement of those goals.

ELIGIBILITY
The Plan is limited to home office and field office senior staff who have a
significant impact on OneBeacon's operating results.

TARGET AWARDS
Target awards for all participants, expressed as a percent of salary, will be
set and approved by the Board of OneBeacon Corporation.

PERFORMANCE MEASURE
The Corporate MIP pool will be established based upon achievement of a 94%
combined ratio for total OneBeacon operations, computed on an adjusted calendar
year basis. This measurement will be used to establish a pool of money to be
allocated to business units and Home Office departments. At a corporate combined
ratio of 94%, the plan will fund an amount equal the sum of each of the plan's
participant's potential award at their target bonus percentage. The OneBeacon
Board of Directors may adjust the size of the pool based on under or over
achievement of the company's target combined ratio and the following objectives:
     -   Successful integration of Atlantic Mutual's commercial business into
         OneBeacon and the achievement of real growth and efficiencies in
         commercial lines.
     -   Successful deployment of our new personal insurance products and
         technology
     -   Continued profitable growth of our specialty businesses, including
         AutoOne and Skylands
     -   Continued claims savings and improved quality

INDIVIDUAL AWARDS
Each business unit will be judged against a number of metrics including, where
appropriate, a combined ratio result target, agreed to in advance with the
President of OneBeacon. Generally these targets will relate to the aggregate
financial plan rolled up by branch and line of business, but the targets will
not always match the plan (in many cases, the targets are more aggressive). If
the combined ratio target is achieved, in conjunction with other business
metrics, the business may be awarded 100% of its indicated share of the
corporate pool. Businesses failing to reach target may or may not, at the
discretion of the President, receive a reduced, partial allocation of the pool.
Businesses exceeding objectives may receive greater than 100% of indicated
allocation. In no event will the sum of the performance adjusted business unit
pools be greater than the performance adjusted company pool.

Within each business, it will be the prerogative of the business leader, with
guidance from and after consultation with the company President, to further
allocate the business's pool amount to the constituent branches, lines of
business and individuals, based upon performance against targets established
within the business. It will be the responsibility of the business leader, with

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guidance from the President, to establish appropriate targets for the
constituent branches, lines of business, departments, or individuals at the
outset of the MIP year.

For corporate or administrative functions that support all or multiple regions
or businesses, MIP individuals will receive allocations from the corporate pool
based upon attainment of their department and individual MIP goals for 2004.

Review and evaluation of performance will be conducted during the first quarter
following the end of the plan year. Incentive payments will be paid once plan
year results have been produced and evaluated.

The salary used to determine the amount of the individual awards will be that in
effect at the end of the plan year (12/31/04).

PLAN PARTICIPATION FOR NEW HIRES
Employees hired during the plan year are eligible to participate in the MIP.
Awards will be pro-rated specifically based on date of hire.

SPECIAL CIRCUMSTANCES
The OneBeacon Board of Directors may, in its sole discretion, also recognize
extraordinary conditions or circumstances in determining payment levels.

In the event of voluntary termination during a plan year or prior to the payment
of awards, other than retirement at the end of the plan year, no incentive
payment will be made. In the event of death or disability, the plan participant
or beneficiary may be considered for a partial award payment.

EFFECT ON BENEFIT PLANS
Amounts paid under the terms of this plan will not be counted for purposes of
determining compensation under any employee benefit plan sponsored by OneBeacon.

PLAN CONTINUATION
Notwithstanding any of the aforementioned, the plan may be amended or
terminated, in whole or in part, at any time, by the Board of Directors.

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