Mainline steam trains in Great Britain
The most famous steam locomotive operating on the British main line is the 1923 built "Flying Scotsman". After being taken into public ownership in 2004, following a decade long refit it returned to mainline service in 2016. The fastest steam locomotive ever built, the 1938 built "Mallard", was also certified for main line operation briefly in the 1980s.
4-6-2
The Great Northern Railway (GNR) and the North Eastern Railway (NER) each built two Pacific types in 1922, later to become the Classes A1/A3 and A2 on the London and North Eastern Railway (LNER). Further examples of these two classes were built by the LNER after 1923.
The GNR Class A1, designed by Sir Nigel Gresley and later rebuilt into the improved Class A3, featured three cylinders and an innovative conjugated valve gear. The class eventually consisted of 79 locomotives. After initial teething problems, it proved to be an excellent design and one of them, the "Flying Scotsman", was the first British locomotive to be officially recorded as reaching .
This speed was surpassed by the streamlined LNER Class A4 of 1935, when no. 2509 "Silver Link" reached on its inaugural run in 1935. Three years later, on 3 July 1938, no. 4468 "Mallard" touched , which is still the world speed record for steam traction. 35 locomotives of the class were built by 1938.