Crossrail's Tunnel-Boring Machines Pictured Under London's Streets

Boris Johnson was at the Crossrail Tunnelling Academy in Ilford Essex on Monday, visiting apprentices and getting a lesson in how to spray concrete.

At £14.8 billion, Crossrail is the biggest construction project in Europe, building a 118 kilometre rail line and 42km of underground lines.

Much of this work is being done underground, right under the feet of oblivious Londoners.

Five tunnel boring machines (TBMs), each one weighing 1,000 tonnes and 148m long, are currently underneath the capitals streets chewing through the earth at a snail-like 100m a week.

Together they will remove six million tonnes of excavated material - enough soil to fill the equivalent of Wembley Stadium to the roof three times.

Progress has to be carefully planned. Not only are there other Tube lines to consider but also secret government tunnels.

Assistant project manager Greg Reichmann, told the Evening Standard: "They don’t tell us exactly where they are, they might just tell us to plan the tunnel a couple of metres left or right."

Some more Crossrail facts:

• Eight new underground stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street, Whitechapel, Canary Wharf and Woolwich will be built
• A new surface station will also be constructed at Custom House
• Crossrail will increase the capacity of London’s rail based public transport network by 10 per cent
• An estimated 200 million people will travel on Crossrail each year
• Phyllis (one of the TBMs) is currently under Hyde Park having completed 2.9km of tunnel and is now heading for Crossrail’s Bond Street Station western ticket hall in Davies Street
• At least two-thirds of all Crossrail excavated material, more than 4.5m tonnes, will be used to create the new RSPB nature reserve at Wallasea Island, creating Europe’s largest man-made coastal reserve