In 1922 Charles Collett, who had recently taken over from George Jackson Churchward as Chief Mechanical Engineer of the Great Western Railway, was faced with the task of preparing a design for a larger and more powerful express passenger locomotive. This was necessitated, firstly, by the increasing weights of trains due to the rising demand for travel. Secondly, there was the desire to reduce journey times to stave off competition, both from rival railway companies such as the London & South Western and the London & North Western, and from other modes of transport. The current front-line GWR express passenger locomotives were the four-cylinder 4-6-0s, the ‘Star’ Class, which had been introduced by Churchward in 1906, when demands on locomotive horsepower were not so onerous.
In his book The Great…