For the purposes of this Act and any other enactment relating to town and country planning, the Land Compensation Act 1961 and the Highways Act 1980, the development plan for any district in Greater London or a metropolitan county (whether the whole or part of the area of a local planning authority) shall be taken as consisting of—
the provisions of the unitary development plan for the time being in force for that area or the relevant part of it, together with a copy of the local planning authority's resolution of adoption or the Secretary of State's notice of approval or, where part of the plan has been adopted and the remainder approved, copies of the resolution and the notice; and
any alteration to that plan, together with a copy of the authority's resolution of adoption, or the Secretary of State's notice of approval, of the alteration or, where part of the alteration has been adopted and the remainder approved, copies of the resolution and the notice.