The London Passenger Transport Board was formed by Act of Parliament in 1933, bringing all of London's underground railways under common control. This allowed large-scale planning to be undertaken, and the 1935-1940 New Works Programme included extensions to what became the Northern Line and major extensions at both ends of the Central London Railway, which became the Central Line. The plan envisaged significant purchases of rolling stock, to service the extended lines, and the 1935 Stock was the forerunner for those purchases. Existing motor cars had a switch compartment behind the drivers cab, occupying nearly one third of the car, and this caused particular problems at busy times. Where two motor cars were coupled together in the centre of the train, there was a length of nearly with no doors for passengers to use.