Following WW2 the GWR addressed the requirements for new locomotives. Among the designs produced under CME F W Hawksworth was a heavy 'shunting engine', based on the successful Collett goods engines and the familiar pannier tank design. The first 10 of these engines were the last new locomotive design built by the GWR before nationalisation, with the class being expanded under Brirtish Railways ownership.
The 94xx panniers were significantly larger than the previous 57xx design, offering improved power and capability, being classified 4F by British Railways. The engines were however heavier, the GWR red route restriction preventing use on many branchlines, but the class quickly took over heavy shunting duties, being able to move an entire train with ease and move empty stock trains in and out of London Paddington far faster then the slow moving diesel shunters. The class was also well suited to many local goods trains on mainline routes as the steam engines' ability to run at a good speed when needed was again an advantage over diesel shunters. The apex of such duties being the regular use of 94xx class engines to haul expresses, including the fastest of them all, the Cheltenham Flyer, between Cheltenham and Gloucester, where the London trains reversed direction.
British Railways expanded the class quickly, ordering batches from several of the private locomotive builders. Why quite so many were ordered has remained quite a mystery. Even the GWR had placed orders for diesel powered shunting engines and later developed the D95xx class 14 0-6-0 diesel with a 40mph maximum speed as a replacement 'branchline' engine. While the diesel locomotives were slow to be delivered and the 94 was an excellent 'stop-gap' one can only suspect political pressure to keep the private builders in business for the number ordered. The result was many had very short lives, 8447 holding the record for the shortest life of possibly any BR locomotive at just 4 years 9 months between building and withdraw.
Two are preserved, Swindon built class leader 9400 can be found at Swindons' Steam museum and 9466, built by Robert Stephenson & Hawthorn, has been returned to service, amply demonstrating the 94xx exceptional power on many heritage railways, taking part in LT/LUL Steam on the Met events and having had a mainline certificate for operation on the national network.