(1)Subject to the provisions of this section, any person authorised by a local authority or by the Secretary of State may at all reasonable times enter any house, premises or building—
(a)for the purpose of survey and examination, where it appears to the local authority or the Secretary of State that survey or examination is necessary in order to determine whether any powers under this Act should be exercised in respect of any house, premises or building;
(b)for the purpose of survey and examination, in the case of any house in respect of which a notice under this Act requiring the execution of works has been served or a closing order, or a demolition order has been made;
(c)for the purpose of survey or valuation, in the case of houses, premises or buildings which the local authority are authorised to purchase compulsorily under this Act;
(d)for the purpose of measuring the rooms of a house in order to ascertain for the purposes of Part VII the number of persons permitted to use the house for sleeping;
(e)for the purpose of ascertaining whether there has been a contravention of any regulation or direction made or given under Part VIII;
(f)for the purpose of ascertaining whether there has been an offence under section 165.
(2)Any person so authorised shall, except where entry is only for the purpose mentioned in paragraph (e) or paragraph (f) of subsection (1), give 24 hours’ notice of his intention to enter any house, premises or building to the occupier thereof and to the owner, if the owner is known.
(3)An authorisation under this section shall be in writing and shall state the particular purpose or purposes for which the entry is authorised.