(1)It shall be a defence in any legal proceedings to recover damages and in any prosecution, in so far as the proceedings or prosecution are or is based on an allegation of a contravention, in relation to any premises, of a provision of this Act or regulations thereunder, to prove that at the time of the alleged contravention the premises were occupied for a purpose that was accomplished before the expiration of a period beginning with the day on which they were occupied for that purpose and of such of the following lengths as is applicable to the circumstances of the case, that is to say, six months if the premises consist of a movable structure, and six weeks if not.
(2)The foregoing subsection shall not apply to a prosecution for an offence consisting in a failure to comply with an obligation imposed under section 49(1) of this Act to notify the appropriate authority that persons would be employed to work in any premises; but in any such prosecution it shall be a defence to prove that the persons in question were employed to work in the premises while they were occupied as mentioned in the foregoing subsection.