s 172 Issue of enforcement notice.
(1) The local planning authority may issue a notice (in this Act referred to as an “ enforcement notice ”) where it appears to them— (a) that there has been a breach of planning control; and (b) that it is expedient to issue the notice, having regard to the provisions of the development plan and to any other material considerations. (2) A copy of an enforcement notice shall be served— (a) on the owner and on the occupier of the land to which it relates; and (b) on any other person having an interest in the land, being an interest which, in the opinion of the authority, is materially affected by the notice. (3) The service of the notice shall take place— (a) not more than twenty-eight days after its date of issue; and (b) not less than twenty-eight days before the date specified in it as the date on which it is to take effect.