Sgt. Murphy is a Kerr Stuart built locomotive, one of a type developed for wartime use. The design was a development of another Kerr Stuart type, the Joffre class, which was mass produced for deployment in the trenches during World War 1.
After the First World War Sgt. Murphy was used by the Admiralty at Beachley Dock at Chepstow, Monmouthshire until being sold to A. H. Richards dealers of Chepstow. It was acquired from Richards in 1921 by Penrhyn Quarry.
In 1932 Sgt. Murphy overturned in the quarry, killing its driver. The accident was attiributed to poor weight distribution, and was rebuilt at the railway's Coed y Parc workshops, with the boiler lowered by more than 7 inches.
It received a new firebox in May 1938 and new side tanks in 1945. In January 1955 it was officially noted as 'scrapped' and left in the scrap line at Coed y Parc.
Sgt. Murphy was purchased by Messrs Pealling and Weaver and moved to Staffordshire in 1964. By 1976, it was at Teddy Boston's Cadeby Rectory by 1976, laid up in a siding in pieces. In 1977 it arrived at the Betws-y-Coed Railway Museum. At the end of 1991 it went to Winson Engineering at Penrhyndeudraeth, where a trailing bogie was added beneath the cab, resulting in the locomotive technically becoming an 0-6-2.
The locomotive resided for a period at the Ffestiniog Railway in North Wales, from which it visited the Teifi Valley Railway in 1994 for Alan George's 100th birthday gala.
In July 1996 it moved to the Teifi Valley Railway. This rare locomotive (the only one of its type remaining in the UK) has since worn a number of impressive liveries, including black and red line black; plain black, and period correct War Department green.