A person authorised by the local housing authority may at all reasonable times, on giving 24 hours' notice to the occupier, and to the owner if the owner is known, enter any premises for the purpose of survey and examination where it appears to the authority that survey or examination is necessary in order to determine whether any powers under this Part should be exercised.
An authorisation for the purposes of this section shall be in writing stating the particular purpose for which it is given and shall, if so required, be produced for inspection by the occupier or anyone acting on his behalf.