(1)In any proceedings for an offence under section 23 of this Act it shall, subject to subsection (2) of this section, be a defence for the person charged to prove—
(a)that the commission of the offence was due to a mistake, or to reliance on information supplied to him, or to the act or default of another person, an accident or some other cause beyond his control, and
(b)that he took all reasonable precautions and exercised all due diligence to avoid the commission of such an offence by himself or any person under his control.
(2)If in any case the defence provided by the preceding subsection involves the allegation that the commission of the offence was due to the act or default of another person or to reliance on information supplied by another person, the person charged shall not, without leave of the court, be entitled to rely on that defence unless, within a period ending seven clear days before the hearing, he has served on the prosecutor a notice in writing, giving such information identifying or assisting in the identification of that other person as was then in his possession.
(3)In proceedings for an offence under section 23 of this Act committed by the publication of an advertisement, it shall be a defence for the person charged to prove that he is a person whose business it is to publish or arrange for the publication of advertisements, and that he received the advertisement for publication in the ordinary course of business and did not know and had no reason to suspect that its publication would amount to an offence under section 23 of this Act.