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
History of the London Underground South London at Kennington, this opening in 1926. Although physically connected, the lines were still officially named the City Railway and Hampstead & Highgate line. The lines were to be known as the Edgware, Highgate and Morden and the Morden-Edgware until finally renamed the Northern line in 1937. Also during the 1920s the original tube gate stock was replaced with 1,460 cars of Standard Stock with air-operating sliding doors, except for the Central line where the cars were refurbished. Busy central London stations were modernised with escalators replacing lifts. Unlike other railway companies in the London area, the Met was