(1)No proceedings for an offence under section 1 above or paragraph 5(3), 6 or 7 of the Schedule to this Act shall be commenced after—
(a)the end of the period of three years beginning with the date of the commission of the offence, or
(b)the end of the period of one year beginning with the date of the discovery of the offence by the prosecutor,
whichever is the earlier.
(2)For the purposes of this section a certificate signed by or on behalf of the prosecutor and stating the date on which the offence was discovered by him shall be conclusive evidence of that fact; and a certificate stating that matter and purporting to be so signed shall be treated as so signed unless the contrary is proved.