LMS Ivatt 4MT 2-6-0

Henry George Ivatt was appointed CME of the LMS in 1946 on the death of Charles Fairburn. The 4MT mogul was Ivatt's larger companion to the very similar 2MT mogul, both designed for ease of maintenance with self-cleaning smokeboxes, rocking grates, and self-emptying ashpans. The 4MT was substantially more powerful than the 2MT, with 17½ in cylinders and 5 ft 3 in driving wheels designed for medium-power mixed-traffic work.

The first 12 engines were built at Horwich in 1947, with the prototype 3000 turned out in distinctive double-chimney form. The class went into full production after nationalisation in 1948, with builds at Horwich, Doncaster, Darlington, and Derby. Total production was 162 engines.

The Ivatt 4MT was so successful that the BR Standard 4MT 2-6-0 (76000 series) of 1953 was effectively a slightly modified version of the same design, sharing many parts. Together the two classes formed a fleet of around 277 medium-power moguls that handled British secondary and branch services through the late steam era.

The Ivatt 4MTs spent their working lives on secondary and branch passenger and freight services across the LMS and Eastern regions. They were popular with crews for free running and ease of maintenance, although the slightly stiff riding at speed earned them the affectionate "Flying Pig" nickname.

Withdrawals began in the early 1960s as branch lines closed and diesel multiple units replaced steam-hauled stopping trains. The class was decimated through the mid-1960s, and the last Ivatt 4MTs were withdrawn from BR service in 1968.

43106 "The Flying Pig" is the most famous preserved Ivatt 4MT, currently in working order at the Severn Valley Railway. It carries the affectionate nickname after the class's general reputation for ungainly appearance.

Three other Ivatt 4MTs survive: 43129, 43137, and 43145. All have been at various stages of overhaul and operation in preservation.

The first 12 engines (1947) were turned out in plain LMS black with smokebox-side number plates. Post-1948 production was painted in BR mixed-traffic lined black with the early lion-and-wheel emblem; from 1956 the late ferret-and-dartboard crest. The preserved 43106 has been outshopped in BR mixed-traffic lined black for most of its preservation career.