The GWR 101 Class consisted of a single experimental 0-4-0T side-tank steam locomotive.

It was built at GWR Swindon Works under the direction of George Jackson Churchward in June 1902.

[1][2] Originally built as an oil-burning locomotive 'on Holden's system'[2][a], it had an unusual boiler containing a firebox constructed as an arched chamber made from fire-bricks, opening to the firetubes in front, and with two oil-burning nozzles at the back.

In 1905, the locomotive was rebuilt as a coal burner, with the cab backplate replaced by a bunker.

[1][2] Despite it being a unique, obscure and short-lived experimental loco, Hornby have been producing a 00 scale model of No.