TR-1(i): NOTIFICATION OF MAJOR INTERESTS IN SHARES

1. Identity of the issuer or the underlying issuer of existing shares to which voting rights are attached (ii):

Inmarsat plc

2. Reason for the notification (please state Yes/No): ( )

An acquisition or disposal of voting rights: (X)

An acquisition or disposal of financial instruments which may result in the acquisition of shares already issued to which voting rights are attached: ( )

An event changing the breakdown of voting rights: ( )

Other (please specify) : (  )

3. Full name of person(s) subject to the notification obligation (iii):

Lehman Brothers International (Europe)

4. Full name of shareholder(s) (if different from 3.) (iv):

N/A

5. Date of the transaction (and date on which the threshold is crossed or  reached if different) (v):

4 September 2008

6. Date on which issuer notified:

    5 September 2008

7. Threshold(s) that is/are crossed or reached:

   7%

8. Notified details:

A: Voting rights attached to shares

B: Financial Instruments

Resulting situation after the triggering transaction (xii)

Total (A+B)

9. Chain of controlled undertakings through which the voting rights and/or the financial instruments are effectively held, if applicable (xv):

N/A

Proxy Voting:

10. Name of the proxy holder:

N/A

11. Number of voting rights proxy holder will cease to hold:

N/A

12. Date on which proxy holder will cease to hold voting rights:

N/A

13. Additional information:

N/A

14. Contact name:                Alison Horrocks

15. Contact telephone number:        020 7728 1626

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