15. Any document required by paragraph 13 or 14 shall at all times during the journey be carried by the person for the time being in charge of the vehicle and shall be handed over by him to any other person to whom he hands over the charge of the vehicle in the course of the journey; and in the case of any document such as is mentioned in paragraph 13, on the unloading of the goods to which the document relates at the premises to which those goods are to be delivered—N.I.
(a)before any of those goods are so unloaded, the document shall be handed over to the buyer; or
(b)if the document cannot be so handed over by reason of the absence of the buyer, it shall be left at some suitable place at those premises;
and if at any time any of the requirements of this paragraph is contravened without reasonable cause, the person in charge of the vehicle at that time shall be guilty of an offence.