17(1)Any officer authorised by a public gas supplier, after seven clear days' notice to the occupier of any premises, or to the owner or lessee of any premises which are unoccupied, may at all reasonable times, on production of some duly authenticated document showing his authority, enter the premises for the purpose of—
(a)placing a new pipe in the place of any existing pipe which has already been lawfully placed ; or
(b)repairing or altering any such existing pipe.
(2)The notice required to be given by sub-paragraph (1) above may, in the case of unoccupied premises the owner or lessee of which is unknown to the supplier and cannot be ascertained after diligent inquiry, be given by affixing it upon a conspicuous part of the premises.
(3)In cases of emergency arising from defects in any pipes entry may be made under sub-paragraph (1) above without the notice required to be given by that sub-paragraph, but the notice shall then be given as soon as possible after the occurrence of the emergency.