LNER Class A4 4468 Mallard is a 4-6-2 ("Pacific") steam locomotive built in 1938 for operation on the London and North Eastern Railway (LNER) at Doncaster Works to a design of Nigel Gresley. Its streamlined, wind tunnel tested design allowed it to haul long distance express passenger services at high speeds. On 3 July 1938, Mallard broke the world speed record for steam locomotives at , which still stands. While in British Railways days regular steam-hauled rail services in the UK were officially limited to a 90 mph 'line speed', before the war, the A4s had to run significantly above 90 mph just to keep schedule on trains such as the Silver Jubilee and The Coronation, with the engines reaching 100 mph on many occasions. Mallard covered almost one and a half million miles (2.4 million km) before it was retired in 1963. The locomotive is long and weighs 165 long tons (168 tonnes, 369,600 lbs), including the tender. It is painted LNER garter blue with red wheels and steel rims. Mallard is now part of the National Collection and preserved at the National Railway Museum in York. History In 1936, Nigel Gresley, the sole chief mechanical engineer of the LNER, ordered a new batch of six 4-6-2 "Pacific" Class A4 engines to be built at Doncaster Works. The A4s were known for their distinct streamlined and aerodynamic design, and designed for hauling long distance express passenger services at high speeds. The first batch comprised four locomotives which entered service in 1935, and had "Silver" in their names as they were to haul the non-stop The Silver Jubilee service between London King's Cross and Newcastle. The six new A4s were named after a bird, influenced by Gresley's fondness of breeding wild birds, and incorporated some modifications to maximise the possibilities of the original streamlined design. This included a new, state-of-the-art double Kylchap chimney and blastpipe, allowing the smoke to be distributed more freely. However, the problem of smoke being dispersed at the front of the locomotive, in turn giving drivers only a narrow viewing window, remained unsolved, and Gresley was determined to find a solution, using Mallard, the 28th A4 locomotive as a test. It was solved after a wooden model at 1/12th of the original size of Mallard was made to undergo smoke tests in a wind tunnel setting, using a tunnel made of plasticine. After a period of