159Power of entry for inspection, &c
Any person authorised in writing stating the particular purpose or purposes for which the entry is authorised, by the local authority or the Minister, may at all reasonable times, on giving twenty-four hours' notice to the occupier and to the owner, if the owner is known, of his intention, enter any house, premises, or buildings—
(a)for the purpose of survey or valuation, in the case of houses, premises, or buildings which the local authority are authorised by this Act to purchase compulsorily; or
(b)for the purpose of survey and examination, in the case of a house in respect of which—
(i)a notice requiring the execution of works has been served under Part II of this Act, or
(ii)a demolition order has been made under Part II or Part III of this Act, or
(iii)a closing order has been made under section eighteen of this Act, or
(iv)a clearance order has been made under Part I11 of this Act, or
(c)for the purpose of survey and examination, where it appears to the authority or Minister that survey or examination is necessary in order to determine whether any powers under this Act should be exercised in respect of the house, premises or building; or
(d)for the purpose of measuring the rooms of a house in order to ascertain for the purposes of Part IV of this Act the number of persons permitted to use the house for sleeping.