GWR 5101 Class Large Prairie 2-6-2T

Charles Collett succeeded George Jackson Churchward as locomotive engineer of the GWR in 1922 and inherited Churchward's 3100 and 5100 large prairie tanks of the early 1900s. By the late 1920s the older engines were nearing the end of their lives, and Collett designed a modern replacement that took the existing Churchward boiler, frames, and motion (which were also shared with the Hall Class and 4300 mogul) and adapted them to a tank-engine layout.

The first 5101 large prairies were built at Swindon Works in 1929. Production continued through the 1930s and 1940s, with a renumbered second series (4100 onwards) coming on stream from 1936. Total production was around 140 engines, making the 5101 one of the most numerous GWR tank classes.

The class was used principally on outer-suburban services from the Birmingham, Cardiff, and London suburban depots. They handled stopping passenger trains of three to six coaches, summer Saturday seaside relief services, and the heavier branch passenger work where their adhesion and pulling power were useful.

The 5101s spent their working lives on outer-suburban services across the Western Region. They were a familiar sight on the Birmingham suburban services into Snow Hill and Moor Street, the Cardiff suburban network, the Cornwall main line's stopping services, and the great majority of GWR outer-suburban work.

Withdrawals began in the early 1960s as branch closures and diesel multiple units removed the work. The class was decimated through 1962 to 1965, with the very last engines surviving to the end of Western Region steam in November 1965.

Ten 5101 large prairies have survived in preservation, more than for almost any other GWR tank class. Survivors include 4144 (Didcot Railway Centre), 4150 (Severn Valley Railway), 4160 (West Somerset Railway), 4115, 5164 (Severn Valley Railway), 5193 (rebuilt to mogul as 9351 at the West Somerset), and 5199 (Llangollen Railway). Several have been in regular working condition for many years and the class is one of the most reliably-represented GWR designs in the heritage railway era.

The class was decimated through the 1960s as Western Region branch lines closed and as diesel multiple units replaced steam-hauled stopping trains. The last 5101 in regular service was withdrawn in 1965 from Croes Newydd, in the very last weeks of Western Region steam.

The class was outshopped from new in GWR-style green with the GWR roundel on the side tanks. British Railways from 1948 painted the class in lined GWR-style green with the early lion-and-wheel emblem; from 1956 the late ferret-and-dartboard crest. Preserved examples have appeared in both GWR-period green and BR plain black liveries during their preservation careers.