The A4s were a class of 4-6-2 steam locomotives, designed by Sir Nigel Gresley for the London and North Eastern Railway in 1935. Their streamlined design gave them high-speed capability as well as making them instantly recognizable. 35 of the class were built to haul express passenger trains on the route from London Kings Cross to the north of England and to Scotland. No.2509 Silver Link locomotive was the first to hit the headlines on a trial trip for the press during the Silver Jubilee year, when it ran 55miles at an average speed of 100mph, with a maximum speed of 112mph at Sandy. On 3rd July 1938, locomotive N.4468 Mallard achieved 126mph descending Stoke Bank between Grantham and Peterborough during brake trials. This set a world speed record for steam traction that still stands to this day. During the Second World War, the side valancing was removed from the streamlining for easier maintenance. Very little outward changes were made to the A4s during their working life, other than the addition of double chimneys and variations of tender. They remained in service until the early 1960s when they were replaced by diesel locomotives. Six locomotives have been preserved, including the famous 'Mallard' locomotive.