Dorothea is a 0-4-0ST 'Quarry Hunslet' built by the Hunslet Engine Company as No. 763 in 1901. Although essentially built to the same design as Covertcoat and Velinheli, she was fitted with an enclosed cab when built. Her working life was spent at the Dorothea Slate Quarry in North Wales, where she worked until around 1942.
Dorothea was abandoned in her shed (which later collapsed around her), with parts of her being sold through the 1960s to enthusiasts for use in the restoration of other locomotives. Her remains were rescued by enthusiast Dave Walker in 1970, who also collected many of the components that had previously been sold to fellow enthusiasts. For most of Dave Walker's ownership, Dorothea was stored in Minsterley, Shropshire, although restoration was never started. Dorothea was moved to Launceston as a pile of components in the 1980s, and was subsequently bought in 1989 by Kay Bowman.
Working in her 'spare' time, Kay carried out a painstaking restoration of Dorothea, a task which was considered impossible by many experts - including Kay's husband! Dorothea was steamed for the first time in preservation in December 2001, although in an incomplete state and using Covertcoat's boiler and saddle tank. Subsequently Kay was awarded the 'John Coiley award for Locomotive Preservation' by the Heritage Railway Association. Since then, Dorothea's own boiler and saddle tank have been repaired, her cab has been refitted and many other parts replaced.
Dorothea was steamed as a complete locomotive for the first time in nearly 70 years on the 13th November 2011, and hauled her first passenger trains at Easter 2012. Following the fitting of air brake equipment, Dorothea entered full time service in October 2012.