Mallard was built on March 3rd, 1938, at Doncaster, where Gordon, Flying Scotsman, and Green Arrow were built. On July the 3rd of that year, while undergoing tests, he established a world speed record of 126 mp/h. He was renumbered to 22 by Edward Thompson's number scheme in 1946, then E22 in the Locomotive Exchange Trials and final to 60022 in British Railways days.
After the decline of steam, Mallard was immediately preserved and put on display at the Museum of British Transport in Clapham, London. In 1975 he was taken to the National Railway Museum, where he remained until 1986, when he was overhauled and taken onto the main line. In 1988, the 50th anniversary of his record, he was retired and put back on display.
It was announced in March 2010 that Mallard was to be moved to Locomotion, the National Railway Museum in Shildon, on June 23rd, 2010. He was pulled by the brand new steam locomotive Tornado; his departure from the museum was a result of the planned redevelopment of the NRM's Great Hall, which was recently cancelled due to unsuccessful funding.
Mallard returned to York in July 2011. He was due to travel to the DB Museum in Nuremberg, Germany for a speed exhibition later in the year, but the event was cancelled. Mallard was one of the engines at Railfest in June 2012.
Mallard celebrated the 75th anniversary of his world speed record in 2013, with all his preserved A4 brothers. As well as Mallard receiving a new coat of LNER Garter Blue, his two transatlantic A4 siblings, No. 60008 Dwight D. Eisenhower and No. 4489 Dominion of Canada were both temporarily shipped back to the United Kingdom to take part in the anniversary (both returned in spring 2014). The event was also attended by fellow siblings No. 60009 Union of South Africa, No. 4464 Bittern, and No. 60007 Sir Nigel Gresley.
- Mallard is best friends with Big Shot.
- Mallard is the brother of Spencer and Olwin since they share the same basis.