By notice dated April 25, 2003, National Grid Transco plc1 (hereinafter “National Grid” or the “Claimant”) requested the institution of an arbitration proceeding against the Argentine Republic (hereinafter “Argentina” or the “Respondent”) under the Arbitration Rules of the United Nations Commission on International Trade Law (hereinafter the “UNCITRAL Rules”) pursuant to the Agreement between the Government of the United Kingdom of Great Britain and Northern Ireland and the Government of the Argentine Republic for the Promotion and Protection of Investments, which was signed on December 11, 1990, and entered into force on February 19, 1993 (the “Treaty”).