Paragraph 20 I1

Except for differences or disputes arising under paragraph 10(2), 10(4), 11(1), 12(1) to (3) and (5) to (11) and 13(1) to (3) and (5) to (11), any difference or dispute arising between the undertaker and National Grid under this Schedule must, unless otherwise agreed in writing between the undertaker and National Grid, be referred to and determined by arbitration in accordance with article 39 (arbitration).