Crossrail, Europe's largest infrastructure project, has reached the halfway point of its construction.

Seven 1,000 tonne tunnelling machines have bored over 29km of new 6.2m diameter tunnels under London, with an eighth machine due to launch next month.

Construction is also advancing on the ten new Crossrail stations and on works above ground west of Paddington and east of Stratford. 10,000 people are currently working on the project.

The £14.8 billion project will add 10% capacity to London's rail network. It will serve 38 stations, connecting Maidenhead and Heathrow in the west with Shenfield and Abbey Wood in the east via central London.

During 2014, Crossrail's major civil engineering and tunnelling works will conclude and the focus will shift towards station construction, fit-out and implementing railway systems within the tunnels and stations. The train operator will then test and refine the systems before trains run from 2018.

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Workers stand in an enormous cavern 40 metres below Stepney Green in the East End of London, in November 2013. The Stepney Green caverns are some of the largest mined caverns ever built in Europe. They are approximately 50m long, 17m wide and 15m high. Stepney Green will have a critical role to play when Crossrail opens; it is where the railway divides with the southeast spur running underground to Canary Wharf, Woolwich and then onto Abbey Wood. The northeast spur runs from Stepney Green through Pudding Mill Lane, Stratford, and then on to Shenfield in EssexCrossrail
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Workers look on after a tunnelling machine broke through into the station structure at Canary Wharf on 11 June, 2013Reuters/Crossrail
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A worker peers around the tunnelling machine after it broke through into Canary Wharf station in June 2013Reuters/Crossrail
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Workers are seen in a shaft on Dean Street during the construction of the Tottenham Court Rad Crossrail stationCrossrail
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Prime Minister David Cameron and London Mayor Boris Johnson visit a Crossrail construction site beneath Tottenham Court Road in London. The largest infrastructure project in Europe has reached the half-way stageReuters
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An aerial view of the Crossrail construction site at Tottenham Court Road in July 2011Wikimedia Commons
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An archaeologist digs out skeletons from the site of the graveyard of the Bethlehem, or Bedlam, hospital next to Liverpool Street StationReuters
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An archaeologist displays a Roman Sestertius brass coin from around AD 30 with an image of the Emperor Hadrian, which was dug out from the Crossrail site near Liverpool Street StationReuters
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The new Crossrail Whitechapel station is pictured under construction, 32 metres below the surface, in February 2013Crossrail
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Tunnelling machine Elizabeth is lowered into a 40m deep shaft at Limmo in East London in October 2012Crossrail
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Workers stand inside a Victorian-era tunnel which is being reconditioned at Crossrail's Albert Dock site in east London, in March 2013Reuters/Crossrail
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Crossrail Apprentice Sam Agyeman stands in the first completed tunnel, from Royal Oak in west London to Farringdon, in November 2013Crossrail
A worker stands in a tunnel under Hanover Square during the construction of Crossrail's new Bond Street station in August 2013Crossrail
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A Crossrail construction site is seen at Farringdon StationCrossrail
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A member of the crew of a bulk freighter prepares his ship to receive tons of earth generated by the construction of Crossrail, at a jetty on the Thames in east LondonReuters