New time-lapse footage has been released showing the progress being made below the capital on Crossrail.
More than five and a half miles of underground tunnels have now been dug.
These pictures show the work that is being carried out at the sites of Finsbury Circus and the new Liverpool Street Station.
The first Crossrail trains are due to run in 2018.
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The mayor believes firefighters who strike for part of a day should lose a full day's pay.
The droppings were all over the place. On the floor, on cooking surfaces. They got everywhere.
The GMB union says the industrial action will create a parking 'free for all' with no one to police yellow lines or parking bays.