based around piston valves. Churchward's valves were 50% larger than anything seen in the UK to that time, travelled 50% further, and were designed to be concealed. The result gave the minimum loss of pressure as steam passed to the cylinders. Churchward's resulting locomotive designs excluded trailing wheels, which maximised adhesion on the South Devon Banks. He was an early adopter in UK locomotive design of superheating, made efficient through the GWR's exclusive use of the high calorific-value steam coal from the South Wales Coalfield. He also adopted large bearing surfaces to reduce wear, something common in North America. Churchward is credited with introducing to Britain several refinements from American and French steam locomotive practice. Among these were the tapered boiler and the casting of cylinders and saddles together, in halves. His choice of outside cylinders for express locomotives was also not standard in Britain for that time. Many elements of British practice were retained, of course. His locomotives for the most part used British plate frames, and the crew was accommodated in typical British fashion. The selection of a domeless boiler was more common to Britain than to the US. 1901 outline scheme In 1901 Churchward produced a scheme of six different locomotive types based on a few standard parts. All would have cylinders with diameter and stroke, piston valves of diameter, and all leading or trailing wheels would be diameter. Locomotive classes corresponding to all these proposals were eventually built, with some differences in the dimensions. Notable locomotives GWR 4-4-0 3700 Class In September 1902 Churchward had a member of the Atbara Class, no. 3405 Mauritius, reboilered with a Belpaire firebox and the first use of a tapered boiler on the GWR. The boiler became the prototype for Churchward's GWR Standard No. 4 boiler. This experiment led to the design of the City class, with the first outshopped from Swindon in March 1903, No. 3433 City of Bath. It was fitted with the final form of the Standard No.4 boiler, with slightly curved sides and a tapered top to the firebox. The class soon became one of the most famous classes of locomotives in the world, when City of Truro became the first engine in the world to haul a train at 100 miles per hour in 1904 (although unauthenticated). Experimental 4-6-0 locomotives In 1901, whilst still assistant to Dean, the GWR board approved Churchward's plan to build