Dark v Western Motor & Carriage Co (Bristol) Ltd The respondents were charged with using a vehicle upon a public road under a general trade licence for a purpose other than a purpose for which the vehicle was authorised to be used under such licence—namely, the towing of a trailer laden with a motor-boat, contrary to the Road Vehicles (Registration and Licensing) Regulations 1924 (SR & O 1924, No 1462), reg 29D, and the Roads Act 1920, s 12.