18.—(1) In any proceedings against a person for an offence under regulation 9, 10, 11 or 12 committed by the publication of an advertisement it shall be a defence for a person to prove that—
(a)he is a person whose business it is to publish or to arrange for the publication of advertisements;
(b)he received the advertisement for publication in the ordinary course of business; and
(c)he did not know and had no reason to suspect that its publication would amount to an offence under the regulation to which the proceedings relate.
(2) In paragraph (1) “advertisement” includes a catalogue, a circular and a price list.