SIP Operation

National Grid PLC
10 May 2007


National Grid plc (NG)

10th May 2007

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

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NG SHARE INCENTIVE PLAN (the 'SIP')

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 30,013 NG ordinary shares under
the scheme was confirmed by the Trustee yesterday, the shares having been
purchased in the market on 8 May, at a price of 776 pence per share, on behalf
of some 2,550 participants.

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

Director                       Shares purchased in SIP
Mark Fairbairn                 16 Ordinary Shares
Steven Holliday                16 Ordinary Shares

The Directors total interests after these events are:

Director                             Resulting total interest
Steven Holliday                      535,301 Ordinary Shares
                                     Nil- B shares - unchanged

Mark Fairbairn                       245,494 Ordinary Shares
                                     B Shares- 6,132- unchanged


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








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