Where by virtue of section 164 of this Act compensation is payable in respect of expenditure incurred in carrying out any work on land, then, if a purchase notice is served in respect of an interest in that land, any compensation payable in respect of the acquisition of that interest in pursuance of the purchase notice shall be reduced by an amount equal to the value of the works in respect of which compensation is payable by virtue of that section.
Where a purchase notice served in respect of an interest in land does not take effect, or does not take effect in relation to a part of the land, by reason that the Secretary of State gives a direction under section 183(3) of this Act, then if, on a claim made to the local planning authority within the time and in the manner prescribed by regulations under this Act it is shown that the permitted development value of that interest (or, as the case may be, of that interest so far as it relates to that part of the land) is less than its existing use value, the local planning authority shall pay to the person entitled to that interest compensation of an amount which (subject to the following provisions of this section) shall be equal to the difference.
If the planning permission which, by the direction referred to in subsection (2) of this section, is required to be granted would be granted subject to conditions for regulating the design or external appearance of buildings, or the size or height of buildings, or for regulating the number of buildings to be erected on the land, the Secretary of State, if it appears to him to be reasonable to do so having regard to the local circumstances, may direct that those conditions shall be disregarded, either altogether or to such extent as may be specified in the direction, in assessing any compensation payable under subsection (2) of this section.
Sections 178 and 179 of this Act shall have effect in relation to compensation under subsection (2) of this section as they have effect in relation to compensation to which those sections apply.
In this section " permitted development value ", in relation to an interest in land in respect of which a direction is given under section 183(3) of this Act, means the value of that interest calculated with regard to that direction, but on the assumption that no planning permission would be granted otherwise than in accordance with that direction, and " existing use value ''; in relation to such an interest, means the value of that interest as (for the purpose of ascertaining the compensation payable on an acquisition thereof in pursuance of the purchase notice) that value would have been assessed in accordance with the provisions of the Acquisition of Land (Assessment of Compensation) Act 1919, as modified by the provisions of sections 51 to 54 of the Act of 1947, if no enactment repealing, modifying or superseding any of those provisions had been passed after the passing of the Act of 1947.