The 45xx Class was a development of Churchward's earlier 44xx Class 2-6-2 tank locomotives.
Almost identical to the original 44xx Class, the only major differences of note to the 45xx were the larger diameter (4'-71/2") driving wheels and the profile in the running plate which was changed to a curved drop end from No.4534 onwards. The increased wheel diameter made the 45xx 2-6-2 generally a more useful engine due to the subsequent increase in speed. They were employed mainly on branchline duties on both passenger and freight trains.
Built originally at Stafford Road Works, Wolverhampton between 1906 and 1908, the first batch of 45xx locomotives were numbered 2161-80 (later 4500-4519). These engines were distinctive in having copper capped chimneys and cast numberplates on their tanks' sides, which were flat topped. The second batch was constructed at Swindon from 1909, nos' 2181-90. In 1912 renumbering took place in the series 4500-4574.
In all, five batches of the Class 45xx were built at Swindon until construction ceased during 1924. The Class was superseded by the Class 4575 three years later. Withdrawals occured as early as 1950, due to the age of the earliest built 45xx's. Currently there are four examples preserved (4555, 4561, 4566 and 4588).