Notification - Directors' Interests on Appointment

4 September 2012

National Grid plc ('National Grid')

Notification of Directors' Interests on Appointment

Following the announcement of Mark Williamson's appointment to the Board with effect from 3 September 2012, National Grid announces that he has notified his interest in a total of 4,726 National Grid plc ordinary shares.

Additionally, in accordance with LR 9.6.13R (3) Mark Williamson has advised that he is a director of International Power Middle East Finance and International Power Humboldt which entered members' voluntary liquidation on 23 January 2012.

National Grid confirms that no further information is required to be disclosed pursuant to LR 9.6.13R of the Listing Rules of the UK Financial Services Authority in relation to the appointment of Mark Williamson as a Director of National Grid plc.

CONTACT

Alice Morgan

Assistant Company Secretary

0207 004 3228