16.—(1) Proceedings for an offence under regulation 14 may, subject to paragraph (2), be commenced within the period of six months from the date on which evidence sufficient in the opinion of the Department to warrant proceedings comes to its knowledge.
(2) No such proceedings shall be commenced by virtue of this regulation more than twelve months after the commission of the offence.
(3) For the purpose of this regulation, a certificate signed on behalf of the Department and stating the date on which evidence sufficient in its opinion to warrant the proceedings came to its knowledge shall be conclusive evidence of that fact.
(4) A certificate stating that matter and purporting to be so signed shall be deemed to be so signed unless the contrary is proved.