(1)For the purposes of this Part, the value of an interest in land, or of an interest in so far as it subsists in particular land, shall be taken to be depreciated by a planning decision (in this section referred to as “the relevant decision”) if, and to the extent to which, that value, calculated in accordance with this section, falls short of what that value so calculated would have been if the relevant decision had been a decision to the contrary effect.
(2)Subject to the following provisions of this section, any such value shall for the purposes of this section be calculated—
(a)as at the time of the relevant decision; but
(b)as affected by that decision, by any grant of planning permission made after that decision and in force immediately before the Secretary of State gives notice of his findings on the claim for compensation in respect of that decision, and by any undertaking to grant planning permission so in force; and
(c)on the assumption that, after the relevant decision and apart from any such permission or undertaking as is mentioned in paragraph (b), planning permission would not be granted for any new development of the land in question, but would be granted for any development of it other than new development.
(3)If in consequence of another planning decision or of an order, being a decision or order made—
(a)before the relevant decision; and
(b)either in respect of the whole or part of the land to which the relevant decision relates or in respect of land which includes the whole or part of that land,
compensation to which this subsection applies has become or becomes payable in respect of that other planning decision or that order, the calculation to be made under this section shall be made as if that other planning decision had been a decision to the contrary effect or, as the case may be, that order had not been made.
(4)Subsection (3) applies—
(a)to any compensation payable under this Part or under Part II or Part V of the 1954 Act or Part VI of the 1962 Act or Part VII of the 1971 Act; and
(b)to so much of any compensation payable under section 107 of this Act, or section 164 of the 1971 Act, or section 118 of the 1962 Act, or under the provisions of those sections as applied by section 108 of this Act, or section 165 of the 1971 Act or section 119 of the 1962 Act respectively, and so much of any compensation to which Part IV of the 1954 Act applied, as is or was payable in respect of loss or damage consisting of depreciation of the value of an interest in land.
(5)In this section “a decision to the contrary effect”—
(a)in relation to a decision refusing permission, means a decision granting the permission subject to such condition (if any) of a description falling within section 121(2) as the authority making the decision might reasonably have been expected to impose if the permission had not been refused; and
(b)in relation to a decision granting the permission subject to conditions, means a decision granting the permission applied for subject only to such of those conditions (if any) as fall within that section.