15(1)Where for the purposes of paragraph 14 the value of any development initiated before a time referred to in that paragraph has to be ascertained with reference to that time, the value of the development shall be calculated in accordance with the provisions of this paragraph.
(2)Subject to the following provisions of this paragraph, the value shall be calculated by reference to prices current at the time in question—
(a)as if the development had not been initiated, but the land had remained in the state in which it was immediately before the development was initiated; and
(b)on the assumption that (apart from the provisions of Part III of this Act, the provisions of Part III of the 1971 Act, the provisions of Part III of the 1962 Act or the provisions of the 1947 Act, as the case may be) the development could at that time lawfully be carried out,
and shall be taken to be the difference between—
(i)the value which in those circumstances the land would have had at that time if planning permission for that development had been granted unconditionally immediately before that time, and
(ii)the value which in those circumstances the land would have had at that time if planning permission for that development had been applied for and refused immediately before that time and it could be assumed that planning permission for that development, and any other new development of that land, would be refused on any subsequent application.
(3)If the development involved the clearing of any land, the reference in sub-paragraph (2)(a) to the state of the land immediately before the development shall be construed as a reference to the state of the land immediately after the clearing of it but before the carrying out of any other operations.
(4)If the development was initiated in pursuance of planning permission granted subject to conditions, sub-paragraph (2) shall apply as if the reference to the granting of permission unconditionally were a reference to the granting of permission subject to the same conditions.
(5)If the permission referred to in sub-paragraph (4) was granted subject to conditions which consisted of, or included, a requirement expressed by reference to a specified period, the reference in that sub-paragraph to the same conditions shall be construed, in relation to the condition imposing that requirement, as a reference to a condition imposing the same requirement in respect of a period of the same duration beginning at the time in question.
(6)In the application of this paragraph to development initiated, but not completed, before the time in question, references to permission for that development shall be construed as references to permission for so much of that development as had been carried out before that time.