The story of the Great Western railcar began with its inventor, C. F. Cleaver of Hardy Railmotors Limited. Hardy's were a subsidiary of the Associated Equipment Co. Ltd. (AEC), and they had provided petrol and diesel engined shunting locomotives in addition to four- and six-wheel drive lorries and tractors through their associated company, the Four Wheel Drive Lorry Company. Cleaver was a man of considerable zeal and realised that the established and successful 130 bhp 6-cylinder AEC diesel engine that was used in London buses and numerous other commercial vehicles, was capable of powering a lightweight self-contained railcar, especially if it utilised streamlining that was popular at the time.
          The body of the first prototype was broadly based on the popular 'Flying Hambuger' diesel unit of Duetsche Reichsbahn, but after windtunnel tests were carried out at the Chiswick laboratory of the London Passenger Transport Board, the body was transformed into a sleek streamlined design with a waisted fontal area.

          Using the 8.85 litre diesel engine, drive was passed to a 5-speed pre-selective gearbox with a fluid flywheel to drive to a pair of axleboxes on one side of the railcar. The 69 seater body was built by Park Royal Coachworks of Willesden, another AEC subsidiary, and measured 62 feet in length and 9 feet in width. Maximum speed was 63 mph with control shared between the ends of the railcar.

          Before completion, the railcar was bought by the Great Western but prior to entering service, it was displayed at the International Commercial Motor Transport Exhibition at Olympia in November 1933. Such was the railcar's popularity at the exhibition, it was estimated that 35,000 people or 53.25 per cent of those that paid for admission to Olympia, visited the railcar. Great publicity, something that the Great Western thrived on, was also given to the railcars movement from Olympia to the GWR sidings at Brentford when the exhibition closed.

          Its first official run on Great Western metals was from Paddington to Reading with a large number of press representatives on the 1st of December 1933, and even AEC jumped on the publicity bandwagon by proclaiming the run as 'an unqualified triumph', and entered public service on the 4th of December working from Slough shed to Windsor and Didcot.

          Within the month however, the railcar was taken out of service for attention to its braking system and method of engine mounting. At the same time, automatic train control was fitted and the car resumed service in February 1934, completing 60,000 miles and transporting 136,000 passengers in its first year alone.

Specifications of GWR Railcar No. 1.

	Engine	(1) 8.85 litre AEC diesel	Length over buffers	63 feet 7 inches
	Bogie centres	40 feet	Bogie wheelbase	7 feet
	Seating capacity	69	Fuel tank	45 gallons
	Weight	24 tons 0 cwt	Maximum speed	63 mph