<PAGE>

                                                                    EXHIBIT 10.6

                             2000 WILLIS AWARD PLAN
                              FOR KEY EMPLOYEES OF
                                  TA I LIMITED

1. PURPOSE OF PLAN

      The 2000 Willis Award Plan for Key Employees of TA I Limited (the "Plan")
is designed:

      (a) to promote the long term financial interests and growth of TA I
Limited (the "Company") and its subsidiaries by attracting and retaining
management personnel with the training, experience and ability to enable them to
make a substantial contribution to the success of the Company's business;

      (b) to motivate management personnel by means of growth-related incentives
to achieve long range goals; and

      (c) to further the alignment of interests of participants with those of
the shareholders of the Company through opportunities for increased share
ownership in the Company.

2. DEFINITIONS. As used in the Plan, the following words shall have the
following meanings:

      (a) "Affiliate" shall mean with respect to any Person, any entity directly
or indirectly controlling, controlled by or under common control with such
Person.

      (b) "Board of Directors" means the Board of Directors of the Company.

      (c) "Change of Control" means (i) a sale of all or substantially all of
the assets of the Company to a Person who is not Kohlberg Kravis Roberts & Co.,
L.P. ("KKR") or an Affiliate of KKR, (ii) a sale by KKR or any of its Affiliates
resulting in more than 50% of the voting shares of the Company being held by a
Person or Group (other than a Person or Group in which KKR or any of its
respective Affiliates has a material interest) or (iii) a takeover,
reconstruction or winding-up involving the Company or KKR or any of its
respective Affiliates resulting in a Person or Group (other than a Person or
Group in which KKR or any of its respective Affiliates has a material interest)
holding more than 50% of the voting ordinary shares of the Company (or the
resulting controlling entity) immediately after any such business combinations;
if and only if any such event results in the inability of the KKR Partnership
(as defined herein) to elect a majority of the Board of Directors of the Company
(or the resulting entity).

      (d) "Committee" means the Compensation Committee of the Board of
Directors.

      (e) "Employee" means a person, including an officer, in the regular
employment of the Company or one of its Subsidiaries who, in the opinion of the
Committee, is, or is expected to be, primarily responsible for the management,
growth or protection of some part or all of the business of the Company.

      (f) "Exchange Act" means the U.S. Securities Exchange Act of 1934, as
amended.

<PAGE>
                                                                               2

      (g) "Fair Market Value" means such value of a Share as determined no less
than annually (or more frequently if the Board of Directors so determines is
required), in good faith by the Board of Directors, after it has taken into
consideration certain factors (including, without limitation, the general
condition of the Company's industry, the historical performance of the Company,
and the Company's financial prospects) and after it has consulted with an
independent investment banking firm selected with the consent of the Group
Executive Committee. In addition, after determining the Fair Market Value, the
value of an individual Participant's shares, on a per share basis, shall not be
reduced to reflect the illiquidity or minority nature associated with such
Participant's shares.

      (h) "Grant" means an award made to a Participant pursuant to the Plan and
described in Paragraph 5, including, without limitation, an award of an U.S.
Incentive Stock Option U.S. Non-Qualified Stock Option, Share Appreciation
Right, Performance Unit, Performance Share or any Other Share-Based Grant or any
combination of the foregoing.

      (i) "Grant Agreement" means an agreement between the Company and a
Participant that sets forth the terms, conditions and limitations applicable to
a Grant.

      (j) "Group" means two or more Persons acting together as a partnership,
limited partnership, syndicate or other group for the purpose of acquiring,
holding or disposing of securities of the Company.

      (k) "KKR Partnership" means Profit-Sharing (Overseas) Limited Partnership,
an affiliate of KKR.

      (l) "Options" means the collective reference to "U.S. Incentive Stock
Options" and "U.S. Non-Qualified Stock Options."

      (m) "Option Agreement" means an agreement between the Company and a
Participant that sets forth the terms, conditions and limitations applicable to
a Option.

      (n) "Ordinary Shares" or "Share" means ordinary shares in TA I Limited.

      (o) "Participant" means an Employee to whom one or more Options have been
granted and such Options have not all been forfeited or terminated under the
Plan.

      (p) "Person" means an individual, partnership, corporation, limited
liability company business trust, joint share company, trust, unincorporated
association, joint venture, governmental authority or other entity of whatever
nature.

      (q) "Share-Based Grants" means the collective reference to the grant of
Share Appreciation Rights, Performance Units, Performance Shares, and Other
Share-Based Grants.

      (r) "Subsidiary" shall mean a body corporate which is a subsidiary of the
Company (within the meaning of Section 736 of the Companies Act 1985).

3. ADMINISTRATION OF PLAN

<PAGE>
                                                                               3


      (a) The Plan shall be administered by the Committee. None of the members
of the Committee shall be eligible to be selected for Grants under the Plan, or
have been so eligible for selection within one year prior thereto; PROVIDED,
HOWEVER, that the members of the Committee shall qualify to administer the Plan
for purposes of Rule 16b-3 (and any other applicable rule) promulgated under
Section 16(b) of the Exchange Act to the extent that the Company is subject to
such rule. The Committee may adopt its own rules of procedure, and action of a
majority of the members of the Committee taken at a meeting, or action taken
without a meeting by unanimous written consent, shall constitute action by the
Committee. The Committee shall have the power and authority to administer,
construe and interpret the Plan, to make rules for carrying it out and to make
changes in such rules. Any such interpretations, rules, and administration shall
be consistent with the basic purposes of the Plan.

      (b) The Committee may delegate to the Chief Executive Officer and to other
senior officers of the Company its duties under the Plan subject to such
conditions and limitations as the Committee shall prescribe except that only the
Committee may designate and make Grants to Participants who are subject to
Section 16 of the Exchange Act.

      (c) The Committee may employ lawyers, consultants, accountants,
appraisers, brokers or other persons. The Committee, the Company, and the
officers and directors of the Company shall be entitled to rely upon the advice,
opinions or valuations of any such persons. All actions taken and all
interpretations and determinations made by the Committee in good faith shall be
final and binding upon all Participants, the Company and all other interested
persons. No member of the Committee shall be personally liable for any action,
determination or interpretation made in good faith with respect to the Plan or
the Grants, and all members of the Committee shall be fully protected by the
Company with respect to any such action, determination or interpretation.

4. ELIGIBILITY

      The Committee may from time to time make Grants under the Plan to such
Employees and in such form and having such terms, conditions and limitations as
the Committee may determine. No Grants may be made under this Plan to
non-employee directors of Company or any of its Subsidiaries. The terms,
conditions and limitations of each Grant under the Plan shall be set forth in a
Grant Agreement, in a form approved by the Committee, consistent, however, with
the terms of the Plan; PROVIDED, HOWEVER, that such Grant Agreement shall
contain provisions dealing with the treatment of Grants in the event of the
termination, death or disability of a Participant, and may also include
provisions concerning the treatment of Grants in the event of a change of
control of the Company.

5. GRANTS

      From time to time, the Committee will determine the forms and amounts of
Grants for Participants. Such Grants may take the following forms in the
Committee's sole discretion:

      (a) U.S. INCENTIVE STOCK OPTIONS - These are stock options within the
meaning of Section 422 of the U.S. Internal Revenue Code of 1986, as amended
("Code"), to purchase Ordinary Shares. In addition to other restrictions
contained in the Plan, an option granted under this


<PAGE>
                                                                               4

Paragraph 5(a), (i) may not be exercised more than 10 years after the date it is
granted, (ii) may not have an option price less than the Fair Market Value of
Ordinary Shares on the date the option is granted, (iii) must otherwise comply
with Code Section 422, and (iv) must be designated as an "Incentive Stock
Option" by the Committee. The maximum aggregate Fair Market Value of Ordinary
Shares (determined at the time of grant) with respect to which Incentive Stock
Options are first exercisable with respect to any participant under this Plan
and any Incentive Stock Options granted to the Participant for such year under
any plans of the Company or any Subsidiary in any calendar year is $100,000.
Payment of the option price shall be made in cash in accordance with the terms
of the Plan, the Option Agreement, and of any applicable guidelines of the
Committee in effect at the time.

      (b) U.S. NON-QUALIFIED STOCK OPTIONS - These are options to purchase
Ordinary Shares which are not designated by the Committee as "U.S. Incentive
Stock Options". At the time of grant the Committee shall determine, and shall
include in the Option Agreement or other Plan rules, the option exercise period,
the option price, and such other conditions or restrictions on the grant or
exercise of the option as the Committee deems appropriate. In addition to other
restrictions contained in the Plan, an option granted under this Paragraph 5(b)
may not be exercised more than 10 years after the date it is granted. Payment of
the option price shall be made in cash in accordance with the terms of the Plan,
the Option Agreement and of any applicable guidelines of the Committee in effect
at the time.

      (c) SHARE APPRECIATION RIGHTS - These are rights that on exercise entitle
the holder to receive the excess of (i) the Fair Market Value of a share of
Ordinary Shares on the date of exercise over (ii) the Fair Market Value on the
date of Grant (the "base value") multiplied by (iii) the number of rights
exercised as determined by the Committee. Share Appreciation Rights granted
under the Plan may, but need not be, granted in conjunction with an Option under
Paragraph 5(a) or 5(b). The Committee, in the Grant Agreement or by other Plan
rules, may impose such conditions or restrictions on the exercise of Share
Appreciation Rights as it deems appropriate, and may terminate, amend, or
suspend such Share Appreciation Rights at any time. No Share Appreciation Right
granted under this Plan may be exercised less than 6 months or more than 10
years after the date it is granted except in the event of death or disability of
a Participant. To the extent that any Share Appreciation Right that shall have
become exercisable but shall not have been exercised or cancelled or by reason
of any termination of employment, shall have become non-exercisable, it shall be
deemed to have been exercised automatically, without any notice of exercise, on
the last day of which it is exercisable, provided that any conditions or
limitations on its exercise are satisfied (other than (i) notice of exercise and
(ii) exercise or election to exercise during the period prescribed) and the
Share Appreciation Right shall then have value. Such exercise shall be deemed to
specify that the holder elects to receive cash and that such exercise of a Share
Appreciation Right shall be effective as of the time of automatic exercise.

      (d) PERFORMANCE UNITS - These are rights to receive at a specified future
date, payment in cash of an amount equal to all or a portion of the value of a
unit granted by the Committee. At the time of the Grant, in the Grant Agreement
or by other Plan rules, the Committee must determine the base value of the unit,
the performance factors applicable to the determination of the ultimate payment
value of the unit and the period over which Company performance will be
measured. These factors must include a minimum performance standard for the
Company below


<PAGE>
                                                                               5



which no payment will be made and a maximum performance level above which no
increased payment will be made. The term over which Company performance will be
measured shall be not less than six months.

      (e) PERFORMANCE SHARES - These are rights to receive at a specified future
date, payment in cash or Ordinary Shares, as determined by the Committee, of an
amount equal to all or a portion of the Fair Market Value for all days that the
Ordinary Shares are traded during the last forty-five (45) days of the specified
period of performance of a specified number of shares of Ordinary Shares at the
end of a specified period based on Company performance during the period. At the
time of the Grant, the Committee, in the Grant Agreement or by Plan rules, will
determine the factors which will govern the portion of the rights so payable and
the period over which Company performance will be measured. The factors will be
based on Company performance and must include a minimum performance standard for
the Company below which no payment will be made and a maximum performance level
above which no increased payment will be made. The term over which Company
performance will be measured shall be not less than six months. Performance
Shares will be granted for no consideration.

      (f) OTHER SHARE-BASED GRANTS - The Committee may make other Grants under
the Plan pursuant to which Ordinary Shares, are or may in the future be
acquired, or Grants denominated in Share units, including ones valued using
measures other than market value. Other Share-Based Grants may be granted with
or without consideration. Such Other Share-Based Grants may be made alone, in
addition to or in tandem with any Grant of any type made under the Plan and must
be consistent with the purposes of the Plan.

6. LIMITATIONS AND CONDITIONS

      (a) The number of Shares available for Grants under this Plan shall be
[NUMBER] Shares; PROVIDED, HOWEVER, that in no event shall the total number of
Shares subject to options and other equity for current and future Participants
exceed 25% of the equity of the Company on a fully diluted basis. Shares subject
to Grants that are forfeited, terminated, canceled or expire unexercised, shall
immediately become available for other Grants.

      (b) No Grants shall be made under the Plan beyond ten years after the
effective date of the Plan, but the terms of Grants made on or before the
expiration of the Plan may extend beyond such expiration. At the time a Grant is
made or amended or the terms or conditions of a Grant are changed, the Committee
may provide for limitations or conditions on such Grant.

      (c) Nothing contained herein shall affect the right of the Company to
terminate any Participant's employment at any time or for any reason. The rights
and obligations of any individual under the terms of his office or employment
with the Company or any Subsidiary shall not be affected by his participation in
this Plan or any right which he may have to participate in it, and an individual
who participates in it shall waive any and all rights to compensation or damages
in consequence of the termination of his office or employment for any reason
whatsoever insofar as those rights arise or may arise from his ceasing to have
rights under or be entitled to exercise any Grant as a result of such
termination.

<PAGE>
                                                                               6


      (d) Other than as specifically provided in the Management and Employee
Shareholders' and Subscription Agreement attached hereto as Exhibit A with
regard to the death of a Participant, no benefit under the Plan shall be subject
in any manner to anticipation, alienation, sale, transfer, assignment, pledge,
encumbrance, or charge, and any attempt to do so shall be void. No such benefit
shall, prior to receipt thereof by the Participant, be in any manner liable for
or subject to the debts, contracts, liabilities, engagements, or torts of the
Participant.

      (e) Participants shall not be, and shall not have any of the rights or
privileges of, shareholders of the Company in respect of any Shares purchasable
in connection with any Grant unless and until certificates representing any such
Shares have been issued by the Company to such Participants.

      (f) No Grant may be exercised during a Participant's lifetime by anyone
other than the Participant except by a legal representative appointed for or by
the Participant.

      (g) Absent express provisions to the contrary, any Grant made under this
Plan shall not be deemed compensation for purposes of computing benefits or
contributions under any retirement plan of the Company or its Subsidiaries and
shall not affect any benefits under any other benefit plan of any kind now or
subsequently in effect under which the availability or amount of benefits is
related to level of compensation. This Plan is not a "Retirement Plan" or
"Welfare Plan" under the U.S. Employee Retirement Income Security Act of 1974,
as amended.

      (h) Unless the Committee determines otherwise, no benefit or promise under
the Plan shall be secured by any specific assets of the Company or any of its
Subsidiaries, nor shall any assets of the Company or any of its Subsidiaries be
designated as attributable or allocated to the satisfaction of the Company's
obligations under the Plan.

7. TRANSFERS AND LEAVES OF ABSENCE

      For purposes of the Plan, unless the Committee determines otherwise: (a) a
transfer of a Participant's employment without an intervening period of
separation among the Company and any Subsidiary shall not be deemed a
termination of employment, and (b) a Participant who is granted in writing a
leave of absence shall be deemed to have remained in the employ of the Company
during such leave of absence.

8. ADJUSTMENTS

      (a) In the event of any increase or variation of the share capital of the
Company, the Committee may make such adjustments as it considers appropriate
under Paragraph 8(b) below.

      (b) An adjustment made under this Paragraph 8(b) shall be to one or more
of the following:

            (i) the number of Shares in respect of which any Option or Other
      Share-Based Grant may be exercised;

            (ii) the price at which Shares may be acquired by the exercise of
      any Option or Other Share-Based Grant;

<PAGE>
                                                                               7


            (iii) where any Option or Other Share-Based Grant has been exercised
      but no Shares have been allotted or transferred pursuant to the exercise,
      the number of Shares which may be so allotted or transferred and the price
      at which they may be acquired.

      (c) An adjustment under Paragraph 8(b) above may have the effect of
reducing the price at which Shares may be acquired by the exercise of an Option
or Other Share-Based Grant to less than their nominal value, but only if and to
the extent that the Board of Directors shall be authorized to capitalise from
the reserves of the Company a sum equal to the amount by which the nominal value
of the Shares in respect of which the Option or Other Share-Based Grant is
exercised and which are to be allotted pursuant to such exercise exceeds the
price at which the same may be subscribed for and to apply that sum in paying up
that amount on the Shares; and so that on exercise of any Option or Other
Share-based Grant in respect of which such a reduction shall have been made the
Board shall capitalise such sum (if any) and apply it in paying up such amount
as aforesaid.

9. EXCHANGE, ACQUISITION, LIQUIDATION OR DISSOLUTION

      (a) In its absolute discretion, and on such terms and conditions as it
deems appropriate, coincident with or after the grant of any Option or Other
Share-Based Grant, the Committee may provide that such Option or Other
Share-Based Grant cannot be exercised after the exchange of all or substantially
all of the assets of the Company for the securities of another corporation, the
acquisition by another corporation of 80% or more of the Company's then
outstanding voting Shares, liquidation or dissolution of the Company, any
variation of the share capital of the Company, and if the Committee so provides,
it may, in its absolute discretion and on such terms and conditions as it deems
appropriate, also provide, either by the terms of such Option or Other
Share-Based Grant or by a resolution adopted prior to the occurrence of such
exchange, acquisition, any variation of the share capital of the Company,
liquidation or dissolution, that, for some period of time prior to such event,
such Option or Other Share-Based Grant shall be exercisable as to all Shares
subject thereto, notwithstanding anything to the contrary herein (but subject to
the provisions of Paragraph 6(b)) and that, upon the occurrence of such event,
such Option or Other Share-Based Grant shall terminate and be of no further
force or effect; PROVIDED, HOWEVER, that the Committee may also provide, in its
absolute discretion, that even if the Option or Other Share-Based Grant shall
remain exercisable after any such event, from and after such event, any such
Option or Other Share-Based Grant shall be exercisable only for the kind and
amount of securities and/or other property, or the cash equivalent thereof,
receivable as a result of such event by the holder of a number of Shares for
which such Option or Other Share-Based Grant could have been exercised
immediately prior to such event.

      (b) If any person becomes bound or entitled to acquire shares in the
Company under sections 428 of 430F of the Companies Act 1985, or if under
section 425 of that Act the Court sanctions a compromise or arrangement proposed
for the purposes of or in connection with a scheme for the reconstruction of the
Company or its amalgamation with any other company or companies, or if the
Company passes a resolution for voluntary winding up, or if an order is made for
the compulsory winding up of the Company, the Committee shall forthwith notify
every Participant thereof and any Option or Other Share-Based Grant may be
exercised within one month of such notification, but to the extent that it is
not exercised within that period shall (notwithstanding any other provision of
this Plan) lapse on the expiration thereof.

<PAGE>
                                                                               8

10. AMENDMENT AND TERMINATION

      The Committee shall have the authority to make such amendments to any
terms and conditions applicable to outstanding Grants as are consistent with
this Plan provided that, except for adjustments under Paragraph 8 or 9 hereof,
no amendment to the disadvantage of any Participant shall be made unless:

      (a) the Committee shall have invited every such Participant to give an
indication as to whether or not he approves the amendment, and

      (b) the amendment is approved by a majority of those Participants who have
given such an indication.

      The Board of Directors may amend, suspend or terminate the Plan except
that no such action, other than an action under Paragraph 8 or 9 hereof, may be
taken which would, without shareholder approval, increase the aggregate number
of Shares available for Grants under the Plan, decrease the price of outstanding
Grants, change the requirements relating to the Committee or extend the term of
the Plan.

11. INTERNATIONAL OPTIONS AND RIGHTS

      The Committee may make Grants to Employees who are subject to the laws of
countries other than the United States or the United Kingdom, which Grants may
have terms and conditions that differ from the terms thereof as provided
elsewhere in the Plan for the purpose of complying with foreign laws.

12. WITHHOLDING TAXES, ALLOTMENT AND TRANSFER

      (a) The Company shall have the right to deduct from any cash payment made
under the Plan any federal, state or local income or other taxes required by law
to be withheld with respect to such payment.

      (b) Within 30 days after an Option has been exercised by any person,
before payment of Performance Shares (if paid in Ordinary Shares) or before
exercise, settlement or payment (if paid in Ordinary Shares) of any Other
Share-Based Grant, the Board of Directors shall allot to such person (or a
nominee for him) or, as appropriate, procure the transfer to him (or a nominee
for him) of the number of Shares in respect of which the option has been
exercised, provided that:

            (i) the Board of Directors considers that the issue or transfer
      thereof would be lawful in all relevant jurisdictions; and

            (ii) in a case where the Company or any Subsidiary ("Group Member")
      is obliged to (or would suffer a disadvantage if it were not to) account
      for any tax (in any jurisdiction) for which the person in question is
      liable by virtue of the exercise of the option and/or for any social
      security, contributions recoverable from the person in question (together,
      the "Tax Liability"), that person has either:


<PAGE>
                                                                               9



                  (A) made a payment to the Group Member of an amount equal to
            the Tax Liability; or

                  (B) entered into arrangements acceptable to that or another
            Group Member to secure that such a payment is made (whether by
            authorizing the sale of some or all of the Shares on his behalf and
            the payment to the Group Member of the relevant amount out of the
            proceeds of sale or otherwise).

      (c) All Shares allotted under this Plan shall rank equally in all respects
with Shares of the same class then in issue except for any rights attaching to
such Shares by reference to a record date prior to the date of the allotment.

13. EFFECTIVE DATE AND TERMINATION DATES

      The Plan shall be effective on and as of the date of its approval by the
Board of Directors and shall terminate ten years later, subject to earlier
termination by the Board of Directors pursuant to Paragraph 10.

14. FINANCIAL ASSISTANCE

      The Company and any Subsidiary may provide money to the trustees of any
trust or any other person to enable them or him to acquire Shares to be held for
the purposes of the Plan, or enter into any guarantee or indemnity for these
purposes or provide financial assistance of any other kind, to the extent
permitted by section 153 of the Companies Act 1985.

15. MISCELLANEOUS

      The masculine pronoun shall include the feminine and neuter, and the
singular the plural, where the context so indicates.