Town and Country Planning Act 1959

2 (1) Where, in connection with a compulsory acquisition to which section one of this Act applies, compensation is payable in respect of an interest in land other than the relevant land, for damage sustained by reason that the relevant land is severed from other land held therewith, or that any other land (whether held with the relevant land or not) is injuriously affected, then, for the purpose of determining whether that other land or any part thereof has an unexpended balance of established development value at any subsequent time, there shall be deducted from the original unexpended balance of established development value (if any) of that other land an amount calculated in accordance with the next following sub-paragraph, and the original balance of that land, or of the part thereof in question, as the case may be, shall be treated as having been reduced or extinguished accordingly immediately before that subsequent time.

(2) The amount referred to in the preceding sub-paragraph is the amount (if any) by which the compensation payable as mentioned in that sub-paragraph exceeds the compensation which would have been so payable if the extent of the damage sustained in respect of the other land in question had fallen to be ascertained on the assumption that planning permission would be granted for development of any class specified in the Third Schedule to the Act of 1947, but would not be granted for any other development of that land.