Transaction in Own Shares

National Grid PLC
28 June 2007




28 June 2007


                                                                           
                               National Grid plc
    Transaction in own shares: Prohibited period share repurchase programme


National Grid plc ('National Grid') announces that it has entered into
irrevocable, non-discretionary arrangements to purchase shares on its own behalf
for cancellation during any prohibited period that National Grid enters into.

Any acquisitions within a prohibited period will be effected within certain
pre-set parameters, and in accordance with both National Grid's general
authority to repurchase shares and Chapter 12 of the Listing Rules which
requires that the maximum price paid be limited to no more than 105 per cent of
the average middle market closing price of National Grid's shares for the 5
dealing days preceding the date of purchase.




CONTACTS

Investors
David Rees     [phone]     [phone] (m)
Richard Smith  [phone]     [phone] (m)
James Waite    [phone]     [phone] (m)





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