Holding in Company

Tullow Oil PLC
20 June 2003


                                  SCHEDULE 10

                   NOTIFICATION OF MAJOR INTERESTS IN SHARES



1. Name of company


Tullow Oil Plc



2. Name of shareholder having a major interest


M&G Investments



3. Please state whether notification indicates that it is in respect of holding
of the shareholder named in 2 above or in respect of a non-beneficial interest
or in the case of an individual holder if it is a holding of that person's
spouse or children under the age of 18


As Above



4. Name of the registered holder(s) and, if more than one holder, the number of
shares held by each of them


Clydesdale Nominees - 40,121,085

Chase Nominees - 6,316,006

Others - 6,472,000



5. Number of shares / amount of stock acquired


N/A



6. Percentage of issued class


N/A



7. Number of shares / amount of stock disposed


N/A



8. Percentage of issued class


N/A



9. Class of security


10p Ord Shares



10. Date of transaction


N/A



11. Date company informed


17/06/03



12. Total holding following this notification


52,909,091



13. Total percentage holding of issued class following this notification


14.01%



14. Any additional information




15. Name of contact and telephone number for queries
Tom Hickey

0207 333 6843



16. Name and signature of authorised company official responsible for making
this notification


Tom Hickey



Date of notification


20 June 2003



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