The GWR 4073 Class 5043 Earl of Mount Edgcumbe is a steam locomotive of the GWR 'Castle' Class, built in March 1936. It was originally named Barbury Castle, and was renamed Earl of Mount Edgcumbe in September 1937 (the name coming from the GWR Dukedog Class no 3200/9000). It had a double chimney and 4 row superheater fitted in October 1958.
Its first shed allocation was Old Oak Common; from June 1952 to February 1956 it was based at Carmarthen, before returning again to Old Oak Common. Like all other steam locomotives based there, with the dieselisation of Cardiff Canton TMD it was transferred to Cardiff East Dock shed in September 1962, its last shed allocation.