After the grouping of 1923 under the Railways Act 1921 there were four large railway companies, each dominating its own geographic area: the Great Western Railway (GWR), the London, Midland and Scottish Railway (LMS), the London and North Eastern Railway (LNER) and the Southern Railway (SR).
Компания была создана в результате национализации в 1948 году Большой четвёрки Британских железнодорожных компаний (Great Western Railway, London, Midland and Scottish Railway, London and North Eastern Railway, Southern Railway).