BR standard class 5
Overview
 
The British Railways Standard Class 5MT 4-6-0
4-6-0
Under the Whyte notation for the classification of steam locomotives, 4-6-0 represents the wheel arrangement of four leading wheels on two axles in a leading truck, six powered and coupled driving wheels on three axles, and no trailing wheels. This wheel arrangement became the second-most popular...

 was one of the standard classes of steam locomotives built by British Railways in the 1950s. 172 were built, essentially being a development of the LMS Stanier Class 5 4-6-0
LMS Stanier Class 5 4-6-0
The London Midland and Scottish Railway's Class 5 4-6-0, almost universally known as the Black Five, is a class of steam locomotive. It was introduced by William Stanier in 1934 and 842 were built between then and 1951...

 ("Black Five").
William Stanier
William Stanier
Sir William Arthur Stanier, FRS was Chief Mechanical Engineer of the London, Midland and Scottish Railway.- Biography :...

's Black Five
LMS Stanier Class 5 4-6-0
The London Midland and Scottish Railway's Class 5 4-6-0, almost universally known as the Black Five, is a class of steam locomotive. It was introduced by William Stanier in 1934 and 842 were built between then and 1951...

 had been the most successful mixed-traffic type in Great Britain. Construction of the Black Fives had started in 1934 and continued past nationalisation to 1951.
 
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