Originally built in 1864 by Fletcher, Jennings & Co. of Whitehaven as an 0-4-0ST, Talyllyn had a short wheelbase and long rear overhang which led to its rapid conversion to an 0-4-2ST. As the more popular of the Talyllyn Railway's two original locos, Talyllyn was in very poor condition by 1945 when he was laid aside. He was rebuilt in 1957-58 by Gibbons Bros. Ltd., but proved problematic and has undergone considerable modification since then, resulting in a much improved performance. Talyllyn is Skarloey's twin, and because of this he was mentioned multiple times in The Railway Series.