Pictures reveal tunnelling marathon under the streets of London London's huge Crossrail development is entering a new phase, with 26 miles of tunnels being dug beneath London - about the same length as the course of the city's famed marathon course. The £14.8bn project, slated for completion in 2018, will connect Maidenhead and Heathrow in the west to Shenfield and Abbey Wood in the east. The developers claim it will increase London's rail capacity by 10 per cent. And new pictures, released today, show the five tunnelling machines carving new paths under the capital, and remodelling old ones, some of which were first used in 1878. Over 7,000 people are working on the dig, which goes on 24 hours a day. It is Europe's biggest construction project, and its five tunnelling machines- Phyllis, Ada, Elizabeth, Victoria and Sophia- have already created more than three miles of tunnels since it started in March 2009. Refurbishment is also underway at the 135-year-old Connaught Tunnel in southeast London, which will be brought back into use for Crossrail. A section of the Royal Docks will soon be drained to allow major works later this year to open the tunnel from above for the first time since its construction in 1878. Andrew Wolstenholme, Crossrail's Chief Executive said: "With 26 miles of new tunnels to be built for Crossrail we are delivering our own London marathon beneath the streets of the capital. This is a huge and complex task with work underway 24 hours a day below London's streets but our first few miles of tunnel are now completed. These new underground images show the scale of transformation taking place beneath London and the essential new transport links being created with every metre of new tunnel built.