s 156 Right to enter without warrant.
(1) Any person duly authorised in writing by a planning authority may at any reasonable hour enter any land— (a) to ascertain whether there is or has been any breach of planning control on the land or any other land; (b) to determine whether any of the powers conferred on a planning authority by sections 127 to 138, 140, 141, 144, 144A, 145 and 147 to 155 should be exercised in relation to the land or any other land; (c) to determine how any such power should be exercised in relation to the land or any other land; (d) to ascertain whether there has been compliance with any requirement imposed as a result of any such power having been exercised in relation to the land or any other land, if there are reasonable grounds for entering for the purpose in question. (2) Any person duly authorised in writing by the Secretary of State may at any reasonable hour enter any land to determine whether an enforcement notice should be issued in relation to the land or any other land, if there are reasonable grounds for entering for that purpose. (3) The Secretary of State shall not so authorise any person without consulting the planning authority. (4) Admission to any building used as a dwellinghouse shall not be demanded as of right by virtue of subsection (1) or (2) unless 24 hours’ notice of the intended entry has been given to the occupier of the building.