Exhibit 10.4.6  ONEBEACONS 2008 MANAGEMENT INCENTIVE PLAN  Purpose  The Management Incentive
Plan (MIP) is an integral part of the total compensation program for managers
and certain senior key individual contributors. Its primary purpose is to focus
attention on 2008 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 are expressed as a percent of salary.  Performance Measures  The Corporate
MIP pool will be established based upon achievement of a 96% GAAP combined
ratio for total OneBeacon operations and the following additional
non-combined ratio objectives:  ·
  Achieve Net Written
  Premium Growth of 9% or better while maintaining underwriting discipline and
  ensuring pricing adequacy.·
  Address current
  over-capitalization.  In particular, 1) improve capital structure of
  run-off business; 2) pay a special dividend of up to $200 million; and 3)
  continue to opportunistically repurchase shares; while 4) maintaining debt to
  total capitalization of 30% or less; and 5) maintaining sufficient capital to
  absorb certain shocks, such as a severe cat loss or significant underperformance
  vs. plan in our investment portfolio.·
  Complete transactions /
  acquisitions that build long-term economic value for OneBeacon.·
  Continue to manage
  aggregate catastrophic exposures for wind, earthquake, flood and terrorism
  and ensure adherence to our strategy of being a low to moderate risk company.  The measurement
against these goals 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
96%, 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
Insurance Group, Ltd. Compensation Committee (the Compensation Committee) may
adjust the size of the pool based on under or over achievement of the companys
target combined ratio and other objectives at its sole discretion.  Individual
Awards  Each
business unit will be judged against a number of metrics including, where
appropriate, a combined ratio 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  1


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 as authorized by the Compensation Committee.  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 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 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 2008.  The salary used to
determine the amount of the individual awards will be that in effect at the end
of the plan year (12/31/08).  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.  Payment of Awards  Unless payment is deferred in accordance with an election made by the
participant in accordance with procedures adopted by OneBeacon Insurance
Company, payment of any MIP award shall be made by the Company no later than 2
1/2 months after the end of the Companys fiscal year in which such MIP award
is earned, but in any event not prior to the Compensation Committees review and
evaluation of performance results following the end of the plan year.  In all cases, no payment
will be made until the Compensation Committee approves the overall corporate
performance factor and performance adjusted MIP pool and no payment will be
made to the CEO or any of the other executive officers without specific
approval from the Committee.  Special
Circumstances  The Compensation
Committee may, in its sole discretion, also recognize extraordinary conditions
or circumstances in determining payment levels.  In the event of
termination prior to the payment of awards, no incentive payments will be
made.  However, in the event of
retirement or reduction in force at or after the end of the plan year, but
before payment is made, incentive payments may be made if approved by the
senior business leader. Payment shall be contingent upon the participant
signing a OneBeacon Agreement and Release as consideration for all incentive
payments. No participant who was terminated prior to the payment of awards due
to a reduction in force may be considered for an incentive payment unless the
participant also signed the Agreement and Release provided to the participant
at the time of termination within the time period specified in the Agreement
and Release. For purposes of the  2


plan, retirement
shall mean termination of service with the company, other than for cause, at
any time after attaining age sixty (60) or termination of service under
circumstances which the Committee deems equivalent to retirement. These
exceptions will be made on a case by case basis. In the event of death or
disability, the plan participant or beneficiary may be considered for a partial
award payment if approved by the senior business leader.  In no way does
eligibility in this plan imply an obligation of payment on the part of
OneBeacon nor should it be construed as a promise of continued employment.  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 Compensation Committee.  3