7.—(1) Proceedings for an offence under regulation 5 may be brought within the period of 6 months beginning with the date on which evidence sufficient in the opinion of the prosecutor to warrant the proceedings came to the prosecutor’s knowledge.
(2) But no such proceedings may be brought more than three years —
(a)after the commission of the offence, or
(b)in the case of a continuous contravention, after the last date on which the offence was committed.
(3) A certificate signed by the prosecutor and stating the date on which such evidence came to the prosecutor’s knowledge is conclusive evidence of that fact; and a certificate to that effect and purporting to be signed is to be treated as being so signed unless the contrary is proved.