SIP Operation

National Grid PLC
11 May 2006


National Grid plc (NG)

11 May 2006
National Grid SHARE INCENTIVE PLAN (the 'SIP')

(Notification of Directors' Interests, pursuant to Section 324(2) of the
Companies Act 1985)

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Under the SIP scheme, operated through Towers Perrin Share Plan Services Limited
as Trustee, employees may acquire NG. ordinary shares by regular monthly
contributions. The current monthly purchase of 44,218 NG. ordinary shares under
the scheme was confirmed by the Trustee yesterday, the shares having been
purchased in the market on 8 May 2006, at a price of 570 pence per share, on
behalf of some 2,800 participants.

The following executive Directors of NG are beneficiaries of the number of
shares purchased on their behalf:

Director               Shares purchased in SIP       Resulting total interest
Steven Holliday        22 Ordinary Shares            487,576 Ordinary Shares
Roger Urwin            22 Ordinary Shares            1,368,026 Ordinary Shares
                                                     281,977 B Shares- unchanged


Contact: D C Forward, Assistant Secretary (0207 004 3226)


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