Any person duly authorised in writing by a local planning authority may at any reasonable hour enter any land—
if there are reasonable grounds for entering for the purpose in question.
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.
The Secretary of State shall not so authorise any person without consulting the local planning authority.
Admission to any building used as a dwellinghouse shall not be demanded as of right by virtue of subsection (1) or (2) unless twenty-four hours' notice of the intended entry has been given to the occupier of the building.