The Passenger Railway Services (Public Ownership) Act 2024, passed last week, allows the government to bring rail contracts back into public ownership.
The government plans to set up a new arms-length entity, Great British Railways (GBR), which will take over service contracts held by private firms as they expire in the coming years.
It also eventually wants GBR Networks to take responsibility for maintaining and improving rail-to-rail infrastructure.
In the 1990s, the responsibility for running train services was handed over to private companies and the use of rail has increased since then.
But many have faced criticism over fares and reliability, with critics saying privatization has led to an inefficient and fragmented system.
Labor set out a manifesto to re-nationalise most rail services within five years.
During the coronavirus pandemic, the government virtually took control of the railways.
Most train companies in England have moved to contracts where they receive a fixed fee for running services, and the taxpayer bears the financial risk.
The four major operators – East Coast Main Line, TransPennine, Northern and South Eastern – have been taken into public control and are being run by the last operator, the Government.
Transport for Wales was brought under the control of the Welsh Government in 2021, and Scotrail was taken over by the Scottish Government the following year.
South Western Railway has more than 1,500 services per week between South West London and the South of England.
It serves a large area in southern England and is a major passenger service in London.