 Various claims exist for the first locomotive to break the barrier, notably the Great Western Railway's "City of Truro" (1904) and the LNER's "Flying Scotsman" (1934).Locomotive power capable of reaching has existed in Britain since 1938, when the LNER's "Mallard" broke the steam locomotive speed record.Despite advances in locomotive engineering, the railway infrastructure was unable to support safe running at such high speeds and, until the mid-1970s, the British railway speed limit remained at .