The class 9F goods locomotive was built from 1954 as the last and most powerful of the standard steam locomotives from British Railways. This was ordered when extensive electrification of the British railway network was still considered realistic and powerful steam locomotives were needed for the transitional period. After Robert Riddles had already developed the 2-10-0 wheel arrangement war locomotives for the War Department, he also developed the 9F. This wheel arrangement was chosen because of the greater adhesive weight after initially planning to develop a locomotive with a 2-8-2 wheel arrangement.
A goal in the development was to realize the greatest possible power, taking into account the British loading gauge and a relatively low axle load. The five driving axles were able to negotiate curves by designing the wheels of the middle coupled axle without a wheel flange and by providing the wheels of the second and fourth axle with thinner wheel flanges. It was soon found that the locomotives ran very well at higher speeds with this wheel arrangement, despite the fact that the driving wheels were only five feet in diameter and there were only two cylinders. In the course of production, the output was further increased with a double chimney. Adaptations such as a Franco-Crosti boiler and mechanical stoker were less successful and were not implemented in large numbers.
Like many more powerful British goods steam locomotives, the 9F also had to be used to pull express trains in heavy holiday traffic, especially on weekends. There are credible reports of runs where the locos hit just over 90 mph. A total of 251 had been built by March 1960. Number 92220 “Evening Star” was the last steam locomotive built for British Railways and was also the 999th standard steam locomotive. This one was not withdrawn even after the steam ban in 1968 and was ran in preservation without interruption until the 1980s. Today it is a static exhibit, while eight more of its sisters, which were retired until 1968, were also preserved and some are still running today. One of these, No. 92203 “Black Prince”, pulled the heaviest train in Great Britain ever hauled by a steam locomotive at 2,178 tons in 1982.
