The 8F class was originally designed by William Stanier of the LMS to improve availability in heavy freight engines and so the design first appeared in 1935. The class was initially chosen by the Ministry of Supply during the Second World War as the standard heavy freight design for war work and 8431 was built by the GWR at Swindon and initially used by them on entering service.
The engine was taken into British Railways ownership upon nationalisation in 1948 and numbered 48431. The locomotive was withdrawn in 1964 and sold for scrap to Woodham Bros. in Barry, South Wales.
The engine languished in the long lines or withdrawn engines until purchased by the KWVR. lt was removed from Barry and arrived by road at Haworth in 1972. On initial purchase the engine was regarded as a long term restoration project by the Society. After much dedication and hard work, however, the engine had been steam-tested by the end of 1974 and re-entered service on the Worth valley in December 1975.
The engine has performed passenger and demonstration freight turns over the years on the KWVR but was finally withdrawn after a second restoration but now is considered, as it was when it first arrived, as a long term restoration project. The locomotive is now on display as a static exhibit in Oxenhope Exhibition shed.