Crossrail, or the Elizabeth Line as it has since been renamed, is due to open in December 2018.
Construction on the £14.8bn project began in 2009, and so far over 100 million working hours have been completed. Some 10 new stations are being built, and 42km of tunnelling has been put down.
As the project is now 85 per cent complete, here's a look back at the track to Crossrail with some of the best pictures of its construction progress along the way.
Crossrail's construction: The best pictures
Trains on the rail service will begin operating in several different stages, with the first Elizabeth Line entering passenger service between Liverpool Street and Shenfield in June.
About 11 Elizabeth Line trains will be rolled out by September along that part of the line. They will initially be 160m long and made up of seven carriages, and will later be extended to nine carriages and the full length of 200m to carry up to 1,500 people.
The line in its entirety will eventually run between Reading and Heathrow in the west, through London and out to Shenfield and Abbey Wood in the east.
Crossrail in numbers
2009 - The year construction of the new railway got underway
15,000 - the number of people who have worked on the project
100m - the number of working hours that have been completed
600 - the number of apprentices that have been recruited for work on the project
30 - the number of years it has taken for a new complete underground line
8 - 1,000 tonne tunnelling machines have bored 26 miles of new rail tunnels under London
10 - new stations have been created in central and Southeast London for Crossrail
3/4 - the proportion of the route that will run above ground on the existing rail network