Exemption in cases involving another's default3

The restrictions imposed by section 52 shall not apply to the sale, offer or exposure for sale or supply of a medicinal product by a person who, having exercised all due diligence, believes on reasonable grounds that the product is a medicinal product—

a

on a general sale list, or

b

which he may lawfully sell, offer or expose for sales or supply, as the case may be, free from the restrictions imposed by section 52, by reason of the exemption conferred by Article 2,

where, due to the act or default of another person, that product is not such a medicinal product, if and so long as the conditions specified in section 53 are fulfilled.