Exhibit 99.1

Monday 30 July 2018
National Grid plc ('National Grid')
AGM poll results
Today, 30 July 2018, the Company held its 2018 Annual General Meeting (“AGM”).

The results of the AGM resolutions, all decided by way of poll, are set out below:
 
Resolution
Votes For
For (% of shares voted)
Votes Against
Against (% of shares voted)
Votes Withheld**
1
To receive the Annual Report and Accounts
2,035,755,228
99.90
1,959,556
0.10
3,843,606
2
To declare a final dividend
2,036,576,253
99.89
2,200,693
0.11
2,794,346
3
To re-elect Sir Peter Gershon
2,018,556,600
99.06
19,238,128
0.94
3,767,563
4
To re-elect John Pettigrew
2,022,043,812
99.22
15,825,951
0.78
3,693,724
5
To re-elect Dean Seavers
2,009,030,535
98.59
28,681,086
1.41
3,851,611
6
To re-elect Nicola Shaw
2,010,404,988
98.66
27,383,666
1.34
3,774,444
7
To re-elect Nora Mead Brownell
2,021,317,050
99.19
16,414,140
0.81
3,831,884
8
To re-elect Jonathan Dawson
2,013,977,209
98.84
23,654,847
1.16
3,931,018
9
To re-elect Therese Esperdy
2,022,956,426
99.28
14,769,460
0.72
3,836,847
10
To re-elect Paul Golby
2,022,620,782
99.26
15,019,174
0.74
3,923,118
11
To re-elect Mark Williamson
2,006,601,106
98.48
30,950,472
1.52
4,011,496
12
To elect Amanda Mesler
2,027,872,509
99.52
9,769,228
0.48
3,923,922
13
To re-appoint the auditors Deloitte LLP
2,031,182,883
99.66
6,886,252
0.34
3,499,999
14
To authorise the Directors to set the auditors' remuneration
2,028,137,212
99.57
8,736,905
0.43
4,683,986
15
To approve the Directors' Remuneration Report excluding the excerpts from the remuneration policy
1,971,102,408
96.94
62,185,956
3.06
8,262,044
16
To authorise the Company to make political donations
1,944,946,459
96.37
73,358,787
3.63
23,223,363
17
To authorise the Directors to allot Ordinary Shares
1,951,224,651
95.73
87,027,019
4.27
3,306,409
18*
To disapply pre-emption rights
2,010,675,740
98.79
24,632,524
1.21
6,228,220
19*
To disapply pre-emption rights for acquisitions
1,974,216,330
96.99
61,294,545
3.01
6,025,195
20*
To authorise the Company to purchase its own Ordinary Shares
2,019,497,033
99.04
19,502,768
0.96
2,552,874
21*
To authorise the Directors to hold general meetings on 14 clear days' notice
1,859,880,749
91.81
165,910,654
8.19
15,762,414
 
* Special resolution
** A "Vote withheld" is not a vote in law and is not counted in the calculation of the votes "For" or "Against" a resolution.


Exhibit 99.1

As required by the Listing Rules of the Financial Conduct Authority, copies of AGM resolutions numbered 18-21 will be made available for inspection from the National Storage Mechanism, situated at: www.morningstar.co.uk/uk/NSM

The complete poll results and details of proxy votes lodged before the meeting will be available shortly on the Company's website http://investors.nationalgrid.com/shareholder-information/agm/2018