Sip Operation

National Grid PLC
11 December 2006


National Grid plc (NG)


Monday, 11th December 2006


(Notifications 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 33,947 NG ordinary shares under
the scheme was confirmed by the Trustee last Friday, 8th December, on the shares
having been purchased in the market on 7th December 2006, at a price of 722
pence per share, on behalf of some 2,700 participants.

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

Director                       Shares purchased in SIP
Steven Holliday                17 Ordinary Shares
Roger Urwin                    17 Ordinary Shares


The Directors total interests after these events are:


Director                             Resulting total interest
Steven Holliday                      535,220 Ordinary Shares
                                     Nil- B shares - unchanged
Roger Urwin                          1,235,177 Ordinary Shares
                                     B Shares- 58,397- unchanged


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





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