Douglas spent most of its working life at RAF Calshot near Southampton, and was later bought by an engineering company called Abelson's. In the early days of preservation, the Talyllyn Railway had contacted this and other similar firms, asking for redundant equipment. Abelson's offered the locomotive to the Talyllyn, and in return they named it after the donor, Douglas Abelson.
Although smaller than the other locomotives on the Talyllyn Railway, it has performed well and was returned to service in 1995, with a new boiler fitted, and turned out in its old Air Ministry Works & Buildings livery.
In recent years Douglas has been painted in standard Talyllyn Railway livery of deep bronze green lined with black borders and yellow lining; however as of 2010 it is painted red, acting as Duncan from the fictional Skarloey Railway. Upon its return in 2013, it will still be in a red livery, but will mainly run as Douglas and running as Duncan during school holidays.
- Douglas is also Duncan's brother.