The project that became Crossrail has origins in the 1943 County of London Plan and 1944 Greater London Plan by Patrick Abercrombie.
The east–west scheme was for a line from Liverpool Street to Paddington/Marylebone with two connections at its western end linking the tunnel to the Great Western Main Line and the Metropolitan line on the Underground.
The City route was shown as a new connection across the City of London linking the Great Northern Route with London Bridge.
Although the idea was seen as imaginative, only a brief estimate of cost was given: £300 million.
A feasibility study was recommended as a high priority so that the practicability and costs of the scheme could be determined.
The central tunnels run from a portal just west of Paddington to Whitechapel, with further tunnelling to Stratford and to Canary Wharf.
There will be new stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street and Whitechapel, with interchanges with the London Underground and other National Rail services.
The project was approved in 2007 and construction began in 2009 on the central section and connections to existing lines that will become part of the route.
An almost entirely new line will branch from the main line at Whitechapel to Canary Wharf, crossing under the River Thames, with a new station at Woolwich and finally connecting with the North Kent Line at the Abbey Wood terminus.
In the east, the line splits at Whitechapel, with one branch running over the existing Great Eastern Main Line via Stratford to Shenfield, and the other branch running through Canary Wharf and emerging from the tunnel at Custom House on a disused part of the North London Line, continuing under the River Thames to Abbey Wood.