In 1923, C. B. Collett, Chief Mechanical Engineer of the Great Weston Railway, introduced the Castle Class express passenger locomotive. In March 1936, locomotive number 5043 'Earl of Mount Edgcumbe' was out shopped from Swindon works. 5043 cost £4,848 with an additional £953 for the 4000 gallon tender.

Originally 5043 was given the name 'Barbury Castle', after an Iron Age hilltop fort, five miles south of Swindon. Renamed in 1937, as ‘Earl of Mount Edgcumbe’, after the Great Weston Railway director. The locomotive remained in service until withdrawn by British Railways in December 1963.

Following storage, she was sold for scrap to the now famous Woodham Brothers of Barry Island in South Wales. This was expected to be the end for 5043. However, she was purchased by 7029 Clun Castle Limited, for use as spare parts. A move to storage at Birmingham Railway Museum in Tyseley, Birmingham followed.

In 1997, Birmingham Railway Museum Trust announced a project to restore 5043 ‘Earl of Mount Edgcumbe’ to main line condition. The 5043 Restoration Fund being set up to finance the work.

On 3rd October 2008, ‘Earl of Mount Edgcumbe’ returned to steam and moved under its own power again after almost 45 years. She returned to the mainline on 16th October 2008. The restoration work being carried out by Tyseley Locomotive Works.