Which locomotive first reached an officially authenticated 100 mph in 1934?

The Flying Scotsman was the locomotive that first reached an officially authenticated 100 mph in 1934. On 30 November that year, LNER locomotive 4472 achieved the speed while hauling a light test train between Leeds and London.

The engine was an LNER Class A3 Pacific designed by Nigel Gresley and built at Doncaster Works in 1923. It became famous through its association with the Flying Scotsman express service between London King’s Cross and Edinburgh Waverley, receiving the service’s name in 1924.

The main mix-up concerns City of Truro. The Great Western Railway locomotive was reported to have reached 100 mph in 1904, but that run was not officially authenticated. Flying Scotsman’s achievement therefore refers to the first officially verified 100-mph locomotive speed, not necessarily the first claim or report of a locomotive travelling that fast. Mallard later set the steam-locomotive speed record in 1938.