Dr. Syn is one of the railway's two Canadian Pacific-style locomotives, built in 1931 by the Yorkshire Engine Co., the other being Winston Churchill and has an identical history of design and build.
Named Black Prince on delivery, Number 10 changed name shortly after the war when Number 9 was re-named Winston Churchill (for obvious patriotic reasons and for display at an exhibition in Canada) and Howey knew that the line could not be without a Doctor Syn (a local fictional hero of smuggling stories).