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.
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.
In the west the route connects with the Great Western Main Line at Paddington and runs to Hayes and Harlington, where it splits.
and joins the main route at Airport Junction, between West Drayton and Hayes and Harlington.
It takes over the Custom House to Woolwich via Connaught tunnel stretch of the former North London Line built by the Eastern Counties and Thames Junction Railway, and connects it with the North Kent Line via a tunnel under the Thames at North Woolwich.
A "dive-under" was constructed at Acton to allow passenger trains to pass slower freight trains leaving and entering a goods yard.
It was completed in July 2016 and was brought into use in 2017.
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.