History of the London Underground to determine the cause. Following the incident, a system that stops a train automatically if the driver fails to brake was introduced at dead-ends on the London Underground. The Northern City Line was connected to British Rail tracks at Finsbury Park in the 1970s. The last tube train ran in October 1975, and British Rail services began in 1976. In 1977, the Piccadilly line was extended from Hounslow to Heathrow Airport, and in 1986 a platform serving Terminal 4 opened on a loop line. The Fleet line through central London was first proposed in 1965, taking over the Bakerloo line's
Airports Commission interests, when invited to complete the Airports Commission's Register of Interests. London, with six commercial airports in its metropolitan area, has the world's busiest airports system. However the question of how to expand the capacity of the system to cope with growing air travel demand is an issue that successive governments have failed to address since the 1950s. A previous commission – the Commission on the Third London Airport chaired by Eustace Roskill – sat between 1968 and 1971 and recommended that a site at Cublington in Buckinghamshire (to the north west of London) should be developed as London's third