Britain operates the most experienced diesel and electric railway in tne world. A century and a half ago she invented the steam engine and introduced a new system of transport; and in only nine years British Rail and the British locomotive industry designed, built and tested enough diesel and electric locomotives to replace fifteen thousand steam engines. The transition from steam to new forms of motive power, and its effects on rallwaymen and passengers, is the subject of this film. Produced in association with the Central Office of Information, the British Locomotive Allied Manufacturers' Association and the British Electrical Manufacturers' Association.