The 57XX/8750 pannier tank locomotives were designed by the GWR’s Chief Mechanical Engineer C.B. Collett. They were intended to replace the ageing fleet of Dean and Churchward tank locomotives, many of which had been converted to pannier tanks from saddle tanks, and the motley collection of locomotives inherited by the GWR at the 1923 grouping. A total of 823 was built by the GWR and later British Railways between 1929 and 1950 making it the most numerous class of locomotive on the GWR and one of the largest class in the United Kingdom. These versatile and puissant tank locomotives were officially designated as light goods and shunting engines by the GWR, but were frequently used for passenger working on branch, suburban, and shorter mainline journeys. The 8750 version was a modification of the original 57XX, the most notable difference being the larger and more modern style of cab.
As a result of the 1955 Modernisation Plan, the 57XX/8750 Class was withdrawn from British Railways service between 1956 and 1966. Nineteen withdrawn locomotives were sold to London Transport and a further six were acquired by the National Coal Board where they achieved a certain celebrity status operating around pits in South Wales after the end of British Railways mainline steam operations in 1968. Sixteen locomotives have survived into preservation.