Voting Rights and Capital Update

23 May 2017

National Grid plc (National Grid)

Voting Rights and Capital Update

On 20 January 2017 National Grid purchased 200,000 of its own ordinary shares of 11 17/43 pence each as part of a buy-back programme announced on 24 November 2016.

As a result of the purchase of its own ordinary shares on 20 January 2017, National Grid held 187,836,542 of its ordinary shares in treasury which equated to 5.0017% of the ordinary shares with voting rights (based on 3,755,440,229 shares with voting rights (excluding treasury shares) as announced on 3 January 2017). This information was disclosable in accordance with DTR 5.5.1.

This announcement does not affect any announcements made by the Company in accordance with DTR 5.6.1R which remain correct.

For the avoidance of doubt, as announced on 22 May 2017, the Company's issued share capital as at 8.00 a.m. on 22 May 2017 consisted of 3,614,401,483 ordinary shares of 12 204/473 pence each of which 173,239,075 were held as treasury shares, leaving a balance of 3,441,162,408 shares with exercisable voting rights.

Contact: D Whincup, Assistant Company Secretary, (0207 004 3209).