Mallard holds the world speed record for steam locomotives, reaching 126 miles per hour in 1938.
The locomotive was London and North Eastern Railway A4 class No. 4468, named Mallard. It made the record-breaking run on 3 July 1938 while descending Stoke Bank near Grantham in Lincolnshire. The train was conducting a high-speed test, and the achievement has remained the accepted record for a steam locomotive.
Mallard was designed by Sir Nigel Gresley, whose streamlined A4 locomotives were built for fast express services on the East Coast Main Line. Its streamlined casing reduced air resistance at high speed, while its powerful three-cylinder arrangement helped it haul heavy trains.
The run placed exceptional stress on the locomotive, and a connecting-rod bearing overheated afterward. Mallard is now preserved at the National Railway Museum in York. Flying Scotsman is famous, but it is not the holder of this speed record.