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.
One of the two eastern sections runs underground from Whitechapel to Stratford, then on the surface on the existing main line.
The service will replace the "Shenfield metro", with key stops at Ilford, Romford (for interchange with London Overground services to Upminster), Gidea Park (where some peak hour trains will start or terminate), and Shenfield.
Due to the size and positioning of the new platforms, Farringdon station will also be connected to Barbican station, and Liverpool Street to Moorgate station.
Positioning a new station at Paddington presented structural design challenges due to its positioning just below Eastbourne Terrace and the station's taxi rank, and within 3 metres of Isambard Kingdom Brunel's 150 year old mainline station.
The need for extra capacity along this corridor is such that the former head of Tf L, Sir Peter Hendy, predicted that the Crossrail lines will be "immediately full" as soon as they open.
The concept of large-diameter tunnels crossing central London to connect Paddington in the west and Liverpool Street in the east was first proposed by railwayman George Dow in The Star newspaper in June 1941.
The central section and a large portion of the line, between Paddington in central London and Abbey Wood in the south-east, are due to open in December 2018, when it will be named the Elizabeth line in honour of Queen Elizabeth II.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.