Talyllyn is Skarloey's twin brother.
Originally built in 1864 by Fletcher, Jennings, and Co. of Whitehaven as an 0-4-0ST, Talyllyn had a short wheelbase and long rear overhang which led to his rapid conversion to a Class C 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.
In April 2014, Talyllyn's right-hand side connecting rod broke, which resulted into him being sent to the Ffestiniog Railway for the connecting rod to be mended, and a bottom-end overhaul to be carried out at the Boston Lodge Works. In August of that year, Talyllyn returned to service, and on 24th of September, he celebrated his 150th birthday in grand style alongside Dolgoch.