The 3F 'Jinty' was an LMS tank engine inspired by the design of a Midland Railway designed tank engine. Henry Fowler saw potential in the Midland Railway 2441 Class which itself would prove so dependable that they would last in service until 1966. The Jinty was a simple design with inside cylinders and belpaire firebox that allowed the locomotive to reach up to 60mph. Locomotives were fitted with steam heating for working short passenger trains, which was a far cry from their initial brief as a shunting engine.
The 3F would be the main shunting and tank engine of the LMS and would find itself serving all over the UK when the class came into the ownership of BR in 1948. The Jintys would prove to be useful engines even after larger freight engines would be introduced with some examples lasting until 1967 in service. 9 examples of the class have been preserved including the last to be withdrawn.
An iconic user of the 3F class was the fairly unique Somerset and Dorset Joint Railway. The SDJR became a part of the LMS in 1923 when the grouping act came into effect however it would not have its identity absorbed into that of the LMS. The SDJR would run its locomotives in either its time honoured 'Prussian Blue' livery with SDJR lettering or SDJR Black. The SDJR took delivery of seven examples of the locomotive in 1928. These locomotives would only stay at the railway for a couple of years, being absorbed into the LMSR in 1930 and redistributed.