Nationalisation. From the start of 1948, the big four were nationalised to form British Railways (latterly British Rail) under the control of the British Transport Commission. Although BR was a single entity, it was divided into six (later five) regional authorities in accordance with the existing areas of operation.

The British equivalent of the word "railroad" is "railway." While the term "railroad" was actually used in Britain in the early 19th century, by the 1830s, the word "railway" became the dominant and now almost exclusive term in the UK. This linguistic split is one of the many differences between British and American English. In the UK, you will hear people refer to the "railway station" instead of the "train station" (though "train station" is becoming more common among younger generations). The physical tracks are often called the "permanent way," and the vehicles that carry passengers are called "carriages" (equivalent to American "coaches" or "cars"). Furthermore, the people who work on maintaining the tracks are traditionally called "platelayers" rather than "track workers." Even the companies themselves use the term, such as "Network Rail" or "Great Western Railway." If you use the word "railroad" in London, you will be understood, but it will immediately mark you as a North American traveler, as "railway" is the term woven into the history, legislation, and daily conversation of the British transport system.