LMS 3-Cylindered Stanier 2-6-4T

The Stanier Class 4P 3-cylinder 2-6-4T was a class of 37 steam tank locomotives, numbered 2500 to 2536, built in 1934 at Derby Works for the London, Midland and Scottish Railway. They were designed specifically for the London, Tilbury and Southend line, where extra power was needed to run heavy outer suburban trains to tight schedules, and the third cylinder gave increased acceleration between the many stops. The inside cylinder and valve gear added maintenance and was judged unnecessary for other duties, so from 1935 the LMS switched to building a very similar but simpler two cylinder design. The class was withdrawn from 1960 to 1962. The first, number 2500, is preserved at the National Railway Museum in York and was loaned to Bury Transport Museum in December 2023.