In 1945 Edward Thompson produced the first Thompson Class L1 tank locomotive at the LNER Darlington Works. Prototype No. 9300 underwent extensive tests before more of the Class were put into production. The remaining 99 of the Class were built between 1947 and 1950 but were not released into traffic until after the formation of British Railways in 1948. The first three of the Class actually entered traffic bearing the LNER numbers 9001, 9002 and 9003 in LNER livery which was changed to British Railways livery and numbering within a few months. The Class was re-numbered twice by British Railways.
Designed for mixed traffic, short distance passenger and freight services, these 2-6-4T locomotives, had a 5'2" diameter driving wheel, two outside 20" x 26" cylinders, a boiler pressure of 225psi and weight 90.89 tons.
The Class did not live up to expectations. While the locomotive had adequate power for hauling heavy freight trains at slower speeds, they were mainly assigned to outer London suburban passenger services where faster speeds and frequent stops wore the engines out very quickly. High maintenance costs led to various modifications on some of the Class in an effort to improve performance and reliability but the modifications did little if anything to help. Very careful handling was required by the crews who soon nicknamed the Class as 'Cement Mixers' due to the loud clanking noise they made.
Line electrification from Liverpool Street in 1960 led to the withdrawal of the first 14 of the Class. By 1962 the entire Class was withdrawn and none have been preserved.
