British Railways (BR), which from 1965 traded as British Rail, was a state-owned company that operated most of the overground rail transport in Great Britain from 1948 to 1997. It was formed from the nationalisation of the Big Four British railway companies, and was privatised in stages between 1994 and 1997. Originally a trading brand of the Railway Executive of the British Transport Commission, it became an independent statutory corporation in January 1963, when it was formally renamed the British Railways Board.The period of nationalisation saw sweeping changes in the railway. A process of dieselisation and electrification took place, and by 1968 steam locomotives had been entirely replaced by diesel and electric traction, except for the Vale of Rheidol Railway (a narrow-gauge tourist line). Passengers replaced freight as the main source of business, and one third of the network was closed by the Beeching cuts of the 1960s in an effort to reduce rail subsidies.

On privatisation, responsibility for track, signalling and stations was transferred to Railtrack (which was later brought under public control as Network Rail) and that for trains to the train operating companies.

The British Rail Double Arrow logo was formed of two interlocked arrows showing the direction of travel on a double track railway and was nicknamed "the arrow of indecision". It is now employed as a generic symbol on street signs in Great Britain denoting railway stations, and is still printed on railway tickets as part of the Rail Delivery Group's jointly managed National Rail brand.

Nationalization (or nationalisation in British English) is the process of transforming privately-owned assets into public assets by bringing them under the public ownership of a national government or state. Nationalization usually refers to private assets or to assets owned by lower levels of government (such as municipalities) being transferred to the state. Nationalization contrasts with privatization and with demutualization. When previously nationalized assets are privatized and subsequently returned to public ownership at a later stage, they are said to have undergone renationalization. Industries often subject to nationalization include the commanding heights of the economy - telecommunications, electric power, fossil fuels, railways, airlines, iron ore, media, postal services, banks, and water - though, in many jurisdictions, many such entities have no history of private ownership.

Nationalization may occur with or without compensation to the former owners. Nationalization is distinguished from property redistribution in that the government retains control of nationalized property. Some nationalizations take place when a government seizes property acquired illegally. For example, in 1945 the French government seized the car-maker Renault because its owners had collaborated with the 1940–1944 Nazi occupiers of France. In September 2021, Berliners voted to expropriate over 240,000 housing units, many of which were being held unoccupied as investment property.Economists can distinguish between nationalization and socialization, which refers to the process of restructuring the economic framework, organizational structure, and institutions of an economy on a socialist basis. By contrast, nationalization does not necessarily imply social ownership and the restructuring of the economic system. By itself, nationalization has nothing to do with socialism - historically, states have carried out nationalizations for various different purposes under a wide variety of different political systems and economic systems.