Mainline steam trains in Great Britain
The most famous steam locomotive operating on the British main line is the 1923 built "Flying Scotsman". After being taken into public ownership in 2004, following a decade long refit it returned to mainline service in 2016. The fastest steam locomotive ever built, the 1938 built "Mallard", was also certified for main line operation briefly in the 1980s.
GE steam turbine locomotives
The General Electric steam turbine locomotives were two steam turbine locomotives built by General Electric (GE) for Union Pacific (UP) in 1938. The two units were streamlined, in length, capable of producing , and reputedly able to attain speeds of . Stylistically, they resembled UP's Pullman-designed M-10003 through M-10006 power units and contemporary Electro-Motive Corporation (EMC) diesel designs.