Holding in Company

Tullow Oil PLC
15 May 2007



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):



TULLOW OIL PLC



2. Reason for the notification (please tick the appropriate box or boxes)



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):



STANDARD LIFE INVESTMENTS LTD



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



VIDACOS NOMINEES



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



10 MAY 2007



6. Date on which issuer notified:



    11 MAY 2007



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



    6%





8. Notified details:



STANDARD LIFE INVESTMENTS LTD DISPOSED OF 500,000 VOTING RIGHTS





A: Voting rights attached to shares


Class/type of shares if possible           Situation previous to the Triggering transaction (vi)
using the ISIN CODE
                                  Number of shares                   Number of voting Rights (viii)
Ord 10p
GB0001500809                      43,095,412                         43,095,412



Resulting situation after the triggering transaction (vii)


Class/type of shares if      Number of shares         Number of voting rights (ix)      % of voting rights
possible using the ISIN CODE
                             Direct                   Direct (x)   Indirect (xi)        Direct      Indirect


Ord 10p                       28,829,997              28,829,997   13,765,415           4.017%      1.918%

GB0001500809




B: Financial Instruments

Resulting situation after the triggering transaction (xii)


Type of         Expiration Date       Exercise/Conversion       Number of voting rights     % of voting rights
financial       (xiii)                Period/ Date (xiv)        that may be acquired if the
instrument                                                      instrument is exercised/
                                                                converted.






Total (A+B)
Number of voting rights        % of voting rights


42,595,412                     5.935%



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



STANDARD LIFE INVESTMENTS LTD



Proxy Voting:



10. Name of the proxy holder:





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





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





13. Additional information:





14. Contact name:



TOM HICKEY, COMPANY SECRETARY





15. Contact telephone number:



0208 996 1000





















This announcement has been issued through the Companies Announcement Service of



                            The Irish Stock Exchange




                      This information is provided by RNS
            The company news service from the London Stock Exchange                   PD