To replace various older tank locomotives in mixed service, Ivatt chose the 2-6-2T wheel arrangement, as this was also very successful on the GWR's “Small Prairies”. He took the 2-6-2T of his predecessor Stanier and made the driving wheels a little smaller. Before nationalization, the LMS only manufactured ten locomotives in their Crewe workshops, with a further 120 being manufactured directly by British Railways there and in Derby. On the one hand, the class formed the basis for the 2-6-0 tender locomotive, which was developed in parallel, and on the other hand for the standard class 2 tank locomotive, which was built from 1953 onwards. The retirements took place between 1962 and 1967, i.e. in the same period as its successor. 