GWR King class 4-6-0 No 6001 King Edward VII waits at Banbury with an express for Paddington in c1935. It had been fitted with a BTH speedometer in 1932 and this required an instrument box to be fixed between the cutaway and the window on the outside of the driver's side of the cab, requiring in turn a cab window that was narrower than usual - a feature retained by 6001 for the rest of its days. The BTH speedometer was soon taken off and was replaced by a standard GWR type by 1937.
Photo: J.N. Hall/Rail Archive Stephenson