The Class 123 was a design of Diesel Multiple Unit built for British Rail in 1963. They were built by British Rail at Swindon Works, and designed like all Swindon units as inter-city sets. Ten of the four-car sets were built and introduced in 1963. The units bear a visible similarity to the British Rail Class 309, however there is no 'relation' here as the two types were built by different manufacturers for different markets. The Class 123's structure and internal construction have much more in common with BR coaching stock (British Rail Mark 1) than they do with other DMU classes. The carriage's underframes are longer and the end gangways are built to a different style. It was also unusual for a first-generation DMU to sport a front end gangway. None of these units survive today. One of the Griddle Cars went on to be used in a Class 309 AC EMU to replace one with a underframe fault.