6U.K.In any proceedings for an offence under section 1 of this Act, it shall be a defence for the person charged to prove that—
(a)in reliance on information supplied by another person, he believed that the article concerned was one which was exempt from hallmarking by virtue of Part II of Schedule 1 to this Act; and
(b)that he could not with reasonable diligence have ascertained that it was not such an article.