50.—The Board and also any authorised undertaker who is authorised under this Act to provide, sell, or let on hire electric lines, fittings, apparatus, and appliances may, subject in the case of an authorised undertaker to the consent of the Board, maintain shops and showrooms for the display, sale and hire of such lines, fittings, apparatus and appliances and conduct displays, exhibitions, and demonstrations of such lines, fittings, apparatus and appliances, and generally do all things (including advertising) incidental to the provision, sale, and letting on hire of such lines, fittings, apparatus, and appliances and the promotion and encouragement of, in the case of the Board, the use generally of such lines, fittings, apparatus and appliances and, in the case of an authorised undertaker, the use of such lines, fittings, apparatus, and appliances in the area of supply of such authorised undertaker.