Mighty Atom was built by Hudswell Clarke of Leeds (Works Number D628) in 1943. The locomotive is diesel-mechanical but retains some steam outline feature such as the funnel.
Delivered to Springfields Works munitions factory outside Preston during World War 2 (10 December 1943) the locomotive was built with all electric circuits in conduit and the engine exhaust passed through a water trap to prevent sparks which could have caused an explosion. D628 worked at what became a nuclear fuel factory until the early 1990s when it and sister locomotive D629 (of 1945) became redundant.
Saved from the scrap man’s torch by a group of then BNFL employees and restored the locomotive was named Mighty Atom on the 50th anniversary of its arrival at Springfields (10 December 1993). It was moved to Steamport, Southport in July 1995 as all rails at the BNFL factory were being lifted and saw brief use at its new home. The mechanical gearbox was too delicate for regular use and she was taken out of service.
Mighty Atom has been recently repainted and prepared as a museum exhibit.