GWR 3252 Duke Class

The GWR 3252 Duke Class was a series of inside-cylinder 4-4-0 express passenger locomotives designed by William Dean and built at Swindon Works from 1895, named after dukes and aristocratic titles and providing the GWR with a capable 4-4-0 express type for the secondary and cross-country express working on its extensive network in the West of England, South Wales, and the Midlands. The Duke Class was built in parallel with Dean's slightly more powerful Bulldog and City 4-4-0 classes that would follow in the early 1900s, and represented the GWR's transition from inside-cylinder 2-4-0 express practice to the 4-4-0 that was becoming the British express standard.

Dean's Duke Class used inside cylinders — a conservative choice that Churchward would subsequently move away from when he took over in 1902 — with 5 ft 7¾ in coupled driving wheels and a parallel boiler of the generous Swindon proportions that had distinguished the GWR's boiler design since the mid-Victorian era. The leading bogie gave better stability at speed than the earlier 2-4-0 types, and the Dukes gave the GWR's secondary express services a significant step forward in performance and reliability.

The Duke Class's story was extended in an unusual way by Collett, who in 1936–39 rebuilt surviving Duke class locomotives by fitting them with Bulldog Class boilers, creating the so-called Dukedog class (GWR 9000 Class) — a hybrid of Duke frames and wheels with Bulldog boilers that gave these elderly locomotives a further lease of life on the Cambrian Coast line in mid-Wales, where their light axle-load was particularly valuable. One Dukedog, No. 9017, is preserved.