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Mallard: The world's fastest steam locomotive

This powerful, aerodynamic masterpiece rocketed to 126mph in 1938, a steam speed record that was never surpassed.

The need for speed

Mallard is an A4 class locomotive designed by Sir Nigel Gresley. The A4s were built to power high-speed trains in the late 1930s, and their shape was honed in a wind tunnel to help them cut through the air as cleanly as possible—making speeds of 120mph and above possible.

Curator with a Camera

Join curator Bob Gwynne as he tells the story of the record attempt and takes you on a tour of this visitor favourite.


About the designer

Born in 1876, Sir Nigel Gresley was an engineering powerhouse with a long list of achievements in his career. He designed A1 Flying Scotsman, the first locomotive to break 100mph in the UK, while Mallard combined a number of technical innovations—from the streamlined casing to the efficient Kylchap exhaust system—to make it a prime candidate for the steam speed record.

Sir Nigel Gresley stands by the locomotive bearing his name
Sir Nigel Gresley stands by the locomotive bearing his name in 1937 (Science Museum Group Collection)

How it came to us

Mallard was selected for preservation thanks to the speed record it achieved and to retain an example of a Gresley A4 Pacific locomotive. Following its retirement from British Rail in 1963 it went on display at the Museum of British Transport in Clapham, before coming to our museum in time for our first day of opening in 1975.