Initially, and for the majority of its history, the BRB operated under the structure inherited from the BTC Railway Executive. Operations were initially divided into six regions – Eastern, London Midland, North Eastern, Western, Southern and Scottish (later rebranded ScotRail). The North Eastern region was merged into the Eastern Region in 1967.
In the 1980s, the BRB moved to a sectoral model based on business activity – InterCity for long-distance passenger trains, Network SouthEast for commuter trains in London, and Regional Railways for short-distance and commuter trains outside the Network SouthEast area. Railfreight was organised separately.
As well as the railway network, for much of its history the BRB also ran ferry services (later as Sealink) and hotels. These were sold in the 1980s.
The final BRB structure (1994–1997) was a shadow form of the future privatised railway industry, becoming a holding company for over 100 subsidiaries, including 25 passenger train operating, six freight, three rolling stock leasing, and a number of track maintenance companies. These were slowly sold during privatisation (the passenger subsidiaries were franchised to private sector concerns).