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
London Underground S Stock (ex-Metropolitan Railway) used with two 1925-built prototype driving motors. In 1925, two driving motor cars were built as prototypes for what would later become the T stock. In the London Passenger Transport Board numbering scheme, they became 2598 and 2599. After the trailer cars were withdrawn from service in the 1940s, the two driving motor cars remained in service on the East London Line, being used with a 1923-built control trailer. These three cars were withdrawn in 1950. London Underground S Stock (ex-Metropolitan Railway) S stock is the designation given to one train of eight cars by London Underground in the 1930s.