British Rail Class 123

The British Rail Class 123 was a design of diesel multiple unit built for British Rail in 1963 at Swindon Works. Ten four-car sets were introduced that year, and they were the last first-generation diesel multiple units built for British Railways. They were first intended for services from the South Coast to Wales, but were used only briefly on Portsmouth to Cardiff and Bristol workings. In service they were concentrated on routes between Swansea, Cardiff, Birmingham, Derby and Crewe and between Cardiff and Bristol, and while still in their original green livery they were trialled between Plymouth and Penzance on the Cornish Main Line as an alternative to locomotive-hauled services. They look much like the Class 309, but the two types were unrelated, built by different manufacturers for different markets.