“[Heathrow] and [Thames Water] shall use all reasonable endeavours to reach agreement […] as to the bases upon which:- (a) the sewage treatment works for the Site would have been operated as from 1989 until 2040 on the assumption that this Agreement and the Interim Arrangement had not been entered into and on the further assumption (if not actually the case) that the Works had not been authorised by the planning authority or the Secretary of State and (b) on a calendar year basis the works comprised in the scheme would be operated, maintained and replaced to the standard applicable thereto […] until 2040 in order to calculate the amount of such additional costs to be paid by [Heathrow] under the provisions of this Clause 7.3.2”
“It being common ground that the matter to be determined by the expert appointed pursuant to Clause 7.3.2.1 of the Agreement is the bases set out in sub-paragraphs (a) and (b) of Clause 7.3.2.1 and that the expert is to make a final, once and for all, determination: (1) whether the said bases include hypothetical mode of operation in the sewage treatment works for the Perry Oaks site as from 1989 until 2040 on the assumptions set out in sub-paragraph (a) of Clause 7.3.2.1 -- as the Claimants contend; or (2) whether the expert should not determine the hypothetical costs of operation at the Site, and whether his determination may provide for the detailed manner or mode of operation of the Site (in accordance with the bases of operation he determines) to be agreed or determined on an annual or other periodic basis to take account of future events, such as changes in regulation or legislation -- as the Defendants contend.”