Section 138(1) of the principal Act (land affected by planning proposals and qualifying for protection under sections 139 to 151 of that Act) shall have effect as if the land specified therein included land which—
(a) is land indicated in a structure plan in force for the district in which it is situated either as land which may be required for the purposes of any functions of a government department, local authority or statutory undertakers, or of the National Coal Board, or as land which may be included in an action area ; or
(b) is land allocated for the purposes of any such functions by a local plan in force for the district or is land defined in such a plan as the site of proposed development for the purposes of any such functions; or
(c) is land in respect of which a compulsory purchase order is in force, where the appropriate authority have power to serve, but have not served, notice to treat in respect of the land ; or
(d) is land on which the Minister of Transport or, in Wales, the Secretary of State proposes to provide a trunk road or a special road and has given to the local planning authority written notice of his intention to provide the road, together with maps or plans sufficient to identify the proposed route of the road.
Subsection (1)(a) above shall not apply to land situated in a district for which a local plan is in force, where that plan—
(a) allocates any land in the district for the purposes of such functions as are mentioned in that paragraph; or
(b) defines any land in the district as the site of proposed development for the purposes of any such functions.
In section 139 of the principal Act (notice requiring purchase of claimant's interest on ground of planning blight), " the relevant date "—
(a) in relation to land mentioned in subsection (1)(c) above, means the date when the order for its compulsory purchase was confirmed or made by the Minister ; and
(b) in relation to land mentioned in subsection (1)(d) above, means the date on which the Minister of Transport or the Secretary of State gave to the local planning authority the written notice specified in that paragraph.
Paragraphs (a) and (b) of subsection (1) above shall have effect instead of paragraphs (a) and (b) of the said section 138(1).