This 0-4-2ST was built in 1921 by Kerr, Stuart & Co. Ltd. for use on the Corris Railway, and was purchased by the Talyllyn in 1951 and named after the TR's former manager. After repairs carried out by the Hunslet Engine Co., the engine entered service on the Talyllyn in 1952 and has proved most successful. From 1958 until 1969 a Giesel ejector was fitted instead of a conventional chimney, the first such installation in the British Isles.

Until 2000 the loco was running in the guise of "Peter Sam", in red livery. It was then repainted into British Railways black, the colour scheme it might have acquired had the Corris line survived a little longer. An extensive overhaul, which has included the fitting of a new boiler, was completed in late May 2004 and the loco returned to public service on Sunday 30th May as "Edward Thomas", in unlined green livery. The loco is now running in the standard TR livery of deep bronze lined with black borders and yellow lining.