Document:

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                                  [LOGO] 0CTEL

EXHIBIT 10.23

          NEW EMPLOYEE'S NAME            Dr Ian McRobbie

                             CONTRACT OF EMPLOYMENT

This document constitutes a formal offer of employment.

Please read details carefully, then indicate your acceptance of this offer by
signing, dating and returning this copy to me.

An additional copy for your retention is enclosed.

                                                 Date  13th August 2001

<PAGE>

1.   NAME OF PARTIES

     EMPLOYER:                  The Associated Octel Company Limited

     EMPLOYEE:                  Dr Ian McRobbie

2.   Your Job Title is:         Chief Technology Officer

3.   Your Normal Place of Work will be:    Global House
                                           Bailey Lane
                                           Manchester M90 4AA

     You will initially be employed at Global House, but as a term of your
     employment you may also be required to work at or from any other of the
     Company's establishments. You may also be transferred or seconded between
     establishments when necessary as required by business needs. Whilst your
     Contract of Employment provides for such transfer or secondment the Company
     will give careful and sympathetic consideration to your personal
     circumstances and career interests.

4.   REMUNERATION

     i)    Your basic salary will be (Pounds)94,401 per annum paid monthly in
           advance by credit transfer. This will be reviewed on 1st March 2002
           and every March thereafter.

     ii)   You will be entitled to participate in the Management Incentive
           Compensation Plan. In your case, the target pay-out would be 40% of
           basic salary, subject to Company and personal performance. The Plan
           normally runs from 1/st/ January to 31/st/ December.

5.   HOURS OF WORK

     The normal hours of work are 38 hours per week exclusive of lunch breaks.

     The Company reserves the right to vary starting and finishing times either
     on a temporary or continuous basis. Any permanent departure from the normal
     working week will be notified in writing. However, irregular variations in
     working hours undertaken in response to operational needs will not be
     formally notified.

     For senior managers, it is recognised that the nature of their roles will
     involve occasionally working extended hours, either during the working week
     or at weekends. This is accepted as a normal part of the working life of a
     global business and does not warrant either extra payment or time off in
     lieu. Where a specific business reason requires working on a public
     holiday, time off in lieu on a day to day basis may be granted by a member
     of the OMB.

6.   COMPANY CAR

     You will be provided with a fully expensed Company car, including private
     fuel. You may take a cash equivalent in lieu of a car. Currently the
     allowance is (Pounds)8,850 per annum. Will you please advise Wendy Thomas
     in Human Resources of your preferred option.

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7.   HOLIDAYS

     For a full year your holiday entitlement is 25 days per annum. The holiday
     year runs from 1st March to the last day in February the following year.

     Service Related Holidays

     You shall be entitled to additional holiday entitlement dependent upon
     completed years of continuous service with the Company on the last day of
     February prior to the holiday year concerned with the following scale:

     Completed Years' Service                        Additional Holidays
            5                                                1 day
           10                                                2 days
           15                                                3 days

     You must arrange the timing of your holidays with your manager so that
     adequate manning cover can be maintained. The minimum holiday that may be
     taken at any time shall normally be one full day. However, you may be
     permitted to take up to 10 half day holidays in any year, or to depart from
     the normal pattern of holidays described above, provided your manager is
     satisfied that such arrangement is in no way detrimental to operational
     needs or to the reasonable opportunity for other staff to take a holiday.

     The Company may, if necessary, nominate up to 1 day out of each year's
     entitlement when holiday must be taken. This may be on a general or
     departmental basis and advance notice will be given wherever possible. Any
     holiday entitlement outstanding at the end of the holiday year will
     normally be forfeited. However, in exceptional circumstances approval to
     carry over part of the entitlement from one holiday year to the next may be
     granted by the appropriate Octel Management Board Member, on the
     recommendation of the Department Manager. During the months of January and
     February each year, staff may bring forward up to 5 days entitlement from
     the ensuring holiday year, by agreement with their manager.

8.   NOTICE

     The Company has the right to terminate your employment by giving you twelve
     months notice in writing. This will not apply in the event of gross
     misconduct. You are required to give the Company six months notice in
     writing of termination of employment. Written notice of termination
     addressed to your manager, may be given on any day and will begin from the
     start of the following day. Failure to give proper notice constitutes a
     breach of contractual obligations.

     The Company will normally require dismissed employees to terminate
     forthwith and may give pay in lieu of notice. Staff may, however, be
     summarily dismissed (i.e. without pay in lieu of notice) when the Company
     is satisfied that an individual is guilty of gross misconduct.

     Should the need arise for redundancies to be declared, the Company reserves
     the right to implement a system for selection based upon principles other
     than `last-in, first-out'.

9.   HEALTHCARE BENEFITS

     You will be entitled to the following healthcare benefits:

     Group Accident Insurance

     You will be covered by the Company's Group Accident Insurance. The
     Company's Insurance Department will be writing to you giving details of the
     Scheme.

<PAGE>

     Octel Healthcare Scheme

     You are entitled to membership for your spouse as well as yourself at
     Company cost. This is a taxable benefit.

11.  SICKNESS ABSENCE

     The Company's scheme entitles you to payment of salary in respect of any
     period of up to one month's absence from work because of certified sickness
     or incapacity.

12.  PERMANENT HEALTH INSURANCE

     You will be entitled, at the Company's expense, to benefit from the
     Company's Permanent Health Insurance Scheme, which provides cover for
     permanent sickness and disability.

13.  MEDICAL EXAMINATIONS

     Employees may be required to submit to medical examinations, including
     biological sampling, which are either statutorily required, or are
     considered by the Company's Medical Officer to be necessary in
     connection with their duties.

     Any other investigations will be conducted on a purely voluntary basis.

     Should an employee, at any time, have been in contact with a person
     suffering from an infectious disease, they should consult the Company's
     Medical Officer before returning to work.

14.  PENSION

     The Company operates a pension scheme for the benefit of employees.

     Membership of the Scheme is available to all established employees who
     are less than 60 years of age.

     The Plan provides retirement pensions and other benefits through a Fund
     which is held under a Trust Deed in order to protect the rights of members.
     The Plan is approved by the Inland Revenue so your contributions are
     allowable for income tax relief at source. Currently, employee
     contributions are set at 2% of pensionable salary.

     The benefits of the Plan are based on Final Salaries with a normal
     retirement date of the first day of the month next following attainment of
     age 65 with voluntary early retirement available, subject to service, from
     age 55.

     A supplement to your package will be agreed with you in the event that your
     salary exceeds the pensions cap.

     All members of the Company's Pension Plan are contracted-out of the State
     Earning Related Pension Scheme (SERPS).

     Details are set out in the attached document but if you require any further
     information concerning your pension arrangements you should contact the
     Human Resources Department at Ellesmere Port.

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     Senior Management Pension Scheme

     You will be able to participate in the Company's Senior Management Scheme,
     which is a non-contributory money purchase plan designed to provide you in
     conjunction with the Company Pension Plan the equivalent of a total of
     1/45/th/ of your pensionable salary for each year of service.

15.  INVENTIONS

     If at any time whilst employed by the Company a member of staff should
     invent, discover or devise individually or jointly with another person(s)
     any invention, design or improvement (collectively called the invention'),
     then the Company's and Employee's rights to such invention(s) are governed
     by current patent legislation.

     The legislation provides for employee inventions whether patentable or not,
     made in the course of an individual's normal duties to belong to the
     Company. In such cases the employee must promptly disclose the invention to
     the Company. Inventions not connected with an employee's work or duties
     belong exclusively to the employee. A further provision generally entitles
     employees to compensation when an invention they have made and which
     belongs to the Company is patented and that patent is of outstanding
     benefit to the Company.

     The Company's Patents Committee, in reviewing the particulars of employees'
     inventions, will take due account of the statutory provisions relating to
     inventions, Patents and Trade Marks. If you need further guidance on this
     section please consult your manager.

16.  SECRECY

     You must not make use of or disclose (either during the period of your
     employment by the Company or at any later date) any information concerning
     the business of the Company, which for the purpose of this paragraph means
     and includes any company or partnership subsidiary to or associated with
     it, or any of its customers except as may be necessary in the proper
     execution of your duties on behalf of the Company or with the prior written
     consent of the Company or to the extent that such information may be
     generally available to the public.

<PAGE>

CONDITIONS OF THIS OFFER

This offer of employment is conditional upon the following conditions being met:

..    Your satisfactory completion of a Company medical examination.

..    Receipt of 2 satisfactory references - One of which must by your current/
     last employer. (We will not approach your current employer until you have
     given us permission to do so).

..    Mutual agreement on a Starting date.

Acceptance:

Please ensure you read this document and sign below to acknowledge receipt and
acceptance of the proposed contract as the terms and conditions governing your
employment with The Associated Octel Company Limited.

Signed:_________________________           Date:_________________________

Signed:_________________________           Date:_________________________<PAGE>

                                  [LOGO] OCTEL

EXHIBIT 10.24

                        EMPLOYEE'S NAME:  PAUL JENNINGS

                             CONTRACT OF EMPLOYMENT

This document constitutes a formal offer of employment.

Please read details carefully, then indicate your acceptance of this offer by
signing, dating and returning this copy to me.

An additional copy for your retention is enclosed.

     Your employment and the terms of this contract will commence on 18/th/
                                  November 2002

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1.    NAME OF PARTIES

      EMPLOYER:              The Associated Octel Company Limited

      EMPLOYEE:              PAUL JENNINGS

2.    Your Job Title is:     VICE PRESIDENT & CHIEF FINANCIAL OFFICER

3.    Your Normal Place of Work will be:      Global House, Manchester

      You will initially be employed at our Manchester office, but as a term of
      your employment you may also be required to work at or from any other of
      the Company's establishments. You may also be transferred or seconded
      between establishments when necessary as required by business needs.
      Whilst your Contract of Employment provides for such transfer or
      secondment the Company will give careful and sympathetic consideration to
      your personal circumstances and career interests.

4.    REMUNERATION

      i)     Your basic salary will be (Pounds)165,000 per annum paid monthly in
             advance by credit transfer. This will be reviewed on 1st March 2003
             and every March thereafter.

      ii)    You will be entitled to participate in the Senior Management Bonus
             Plan. In your case, the target pay-out would be 40% of basic
             salary, subject to Company and personal performance. The Plan
             normally runs from 1/st/ January to 31/st/ December.

5.    HOURS OF WORK

      The normal hours of work are 38 hours per week exclusive of lunch breaks.

      The Company reserves the right to vary starting and finishing times either
      on a temporary or continuous basis. Any permanent departure from the
      normal working week will be notified in writing. However, irregular
      variations in working hours undertaken in response to operational needs
      will not be formally notified.

      For senior managers, it is recognised that the nature of their roles will
      involve occasionally working extended hours, either during the working
      week or at weekends. This is accepted as a normal part of the working life
      of a global business and does not warrant either extra payment or time off
      in lieu. Where a specific business reason requires working on a public
      holiday, time off in lieu on a day to day basis may be granted by a member
      of the Octel Management Board.

6.    COMPANY CAR

      You will be provided with a fully expensed Company car, including private
      fuel. You may take a cash equivalent in lieu of a car. Currently the
      allowance is (Pounds)13,650 per annum. Will you please advise Wendy Thomas
      in Human Resources of your preferred option.

                                                                               2

<PAGE>

7.    HOLIDAYS

      For a full year your holiday entitlement is 25 days per annum. The holiday
      year runs from 1st March to the last day in February the following year.

      Service Related Holidays
      You shall be entitled to additional holiday entitlement dependent upon
      completed years of continuous service with the Company on the last day of
      February prior to the holiday year concerned with the following scale:

      Completed Years' Service                        Additional Holidays
      ------------------------                        -------------------
                 5                                           1 day
                 10                                          1 day
                 15                                          1 day

      You must arrange the timing of your holidays with your manager so that
      adequate manning cover can be maintained. The minimum holiday that may be
      taken at any time shall normally be one full day. However, you may be
      permitted to take up to 10 half day holidays in any year, or to depart
      from the normal pattern of holidays described above, provided your manager
      is satisfied that such arrangement is in no way detrimental to operational
      needs or to the reasonable opportunity for other staff to take a holiday.

      The Company may, if necessary, nominate up to 1 day out of each year's
      entitlement when holiday must be taken. This may be on a general or
      departmental basis and advance notice will be given wherever possible. Any
      holiday entitlement outstanding at the end of the holiday year will
      normally be forfeited. However, in exceptional circumstances approval to
      carry over part (5 days maximum) of the entitlement from one holiday year
      to the next may be granted by the appropriate Octel Management Board
      Member, on the recommendation of the Department Manager and HR Department.
      During the months of January and February each year, staff may bring
      forward up to 5 days entitlement from the ensuing holiday year, by
      agreement with their manager.

8.    NOTICE

      The Company has the right to terminate your employment by giving you
      twelve months notice in writing. This will not apply in the event of gross
      misconduct. You are required to give the Company six months notice in
      writing of termination of employment. Written notice of termination
      addressed to your manager, may be given on any day and will begin from the
      start of the following day. Failure to give proper notice constitutes a
      breach of contractual obligations.

      The Company will normally require dismissed employees to terminate
      forthwith and may give pay in lieu of notice. Staff may, however, be
      summarily dismissed (i.e. without pay in lieu of notice) when the Company
      is satisfied that an individual is guilty of gross misconduct.

      Should the need arise for redundancies to be declared, the Company
      reserves the right to implement a system for selection based upon
      principles other than `last-in, first-out'.

9.    HEALTHCARE BENEFITS

      You will be entitled to the following healthcare benefits:

      Group Accident Insurance
      You will be covered by the Company's Group Accident Insurance. The
      Company's Insurance Department will be writing to you giving details of
      the Scheme.

                                                                               3

<PAGE>

      Octel Healthcare Scheme
      You are entitled to membership for your spouse as well as yourself at
      Company cost. This is a taxable benefit.

10.   SICKNESS ABSENCE

      The Company's scheme entitles you to payment of salary in respect of any
      period of up to one month's absence from work because of certified
      sickness or incapacity.

11.   MEDICAL EXAMINATIONS

      Employees may be required to submit to medical examinations, including
      biological sampling, which are either statutorily required, or are
      considered by the Company's Medical Officer to be necessary in connection
      with their duties.

      Any other investigations will be conducted on a purely voluntary basis.

      Should an employee, at any time, have been in contact with a person
      suffering from an infectious disease, they should consult the Company's
      Medical Officer before returning to work.

12.   PENSION

      The Company operates a defined contribution Group Personal Pension for the
      benefit of employees.

      Membership of this scheme is available to all UK employees up to the
      Company's normal retirement date.

      The Company will contribute 9% of salary up to the salary cap
      ((Pounds)97,200) and you will pay 5%. The Company will then match 100% up
      to the Inland Revenue maximum (i.e., a total of 17.5% of salary). Above
      the cap you will be eligible to join a plan in which the Company will
      contribute 20% of salary above the cap, or provide a salary supplement of
      the same level.

13.   INVENTIONS

      If at any time whilst employed by the Company a member of staff should
      invent, discover or devise individually or jointly with another person(s)
      any invention, design or improvement (collectively called 'the
      invention'), then the Company's and Employee's rights to such invention(s)
      are governed by current patent legislation.

      The legislation provides for employee inventions whether patentable or
      not, made in the course of an individual's normal duties to belong to the
      Company. In such cases the employee must promptly disclose the invention
      to the Company. Inventions not connected with an employee's work or duties
      belong exclusively to the employee. A further provision generally entitles
      employees to compensation when an invention they have made and which
      belongs to the Company is patented and that patent is of outstanding
      benefit to the Company.

      The Company's Patents Committee, in reviewing the particulars of
      employees' inventions, will take due account of the statutory provisions
      relating to inventions, Patents and Trade Marks. If you need further
      guidance on this section please consult your manager.

                                                                               4

<PAGE>

14.   SECRECY

      You must not make use of or disclose (either during the period of your
      employment by the Company or at any later date) any information concerning
      the business of the Company, which for the purpose of this paragraph means
      and includes any company or partnership subsidiary to or associated with
      it, or any of its customers except as may be necessary in the proper
      execution of your duties on behalf of the Company or with the prior
      written consent of the Company or to the extent that such information may
      be generally available to the public.

15.   PERSONAL DATA

      Octel needs to keep information about you for purposes connected with your
      employment. The sort of information we will hold includes information for
      payroll purposes, references, contact names and addresses and other
      personal details relating to your career with us. Some of this information
      may also be processed by other organisations on our behalf.

      We believe these uses are consistent with the principles of the Data
      Protection Act 1998. The information we hold will be for our management
      and administrative use only but we may, from time to time, need to
      disclose some information we hold about you to relevant third parties (eg
      The Inland Revenue). We may also transfer information about you to another
      Octel company/location (which may be outside of the European Economic
      Area) solely for purposes connected with your career or the management of
      our business. You agree to us keeping the information for these purposes
      throughout your employment and following its termination.

      You also agree to us keeping information about your health for the
      purposes of compliance with our health and safety and occupational health
      obligations; considering how your health affects your ability to do your
      job and, if you are or become disabled, whether you require any reasonable
      adjustments to be made to assist you at work; or in relation to the
      administration of insurance, pension, sick pay and any other related
      benefits in force from time to time.

      You agree to us holding details of any unspent convictions that may affect
      your suitability for employment in addition to any other personal data we
      require to ensure compliance with our Equal Opportunities Policy (eg race
      and/or ethnic origin).

16.   STOCK OPTIONS

      You will be eligible to participate in the executive Stock Option Plan
      which is determined annually by the Compensation Committee of the Board.

17.   RELOCATION

      The Company will cover the costs of the sale of the US property and
      purchase in the UK as detailed in the Relocation Policy for New Starters.
      A 10% disturbance allowance will apply. Any resulting personal tax
      liability will be paid by the Company.

                                                                               5

<PAGE>

CONDITIONS OF THIS OFFER

This offer of employment is conditional upon the following conditions being met:

..     Your satisfactory completion of a Company medical examination.

..     Receipt of 2 satisfactory references - One of which must by your
      current/last employer. (We will not approach your current employer until
      you have given us permission to do so).

..     Sight of your birth certificate and copies of qualification certificates
      for our records.

Acceptance:

Please ensure you read this document and sign below to acknowledge receipt and
acceptance of the proposed contract as the terms and conditions governing your
employment with The Associated Octel Company Limited.

Signed:     _________________________________________ Date: ____________________
            On behalf of the Company

Signed:     _________________________________________ Date: ____________________

                                                                               6

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