Exhibit 12(a)

CERTIFICATIONS PURSUANT TO
18 U.S.C. SECTION 1350
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

      In connection with the Annual Report of National Grid Transco plc (the “Company”) on Form 20-F for the period ending March 31, 2003 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Roger Urwin, Group Chief Executive of the Company, certify, to the best of my knowledge, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of section 13(a) or 15 (d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Roger Urwin

Roger Urwin

Group Chief Executive

June 11, 2003

      In connection with the Annual Report of National Grid Transco plc (the “Company”) on Form 20-F for the period ending March 31, 2003 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Stephen Lucas, Group Finance Director of the Company, certify, to the best of my knowledge, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of section 13(a) or 15 (d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Stephen Lucas

Stephen Lucas

Group Finance Director

June 11, 2003