Crossrail's seventh boring machine has set off as progress reaches close to the halfway stage.

The machine will start at Pudding Mill Lane, Stratford and start a 1.7 mile tunnel towards Stepney Green. It will be joined by the eighth machine, which will create a second tunnel. These will form a section of the twin-bore tunnels that make up 13 miles of the Crossrail project. After this, only the two shortest tunnels - each 900 metres in length - will be left for construction.

Transport minister Stephen Hammond said the launch of the machine "marks another significant milestone in the Crossrail project, as we approach the halfway stage in our tunnelling marathon".

Progress comes shortly after drilling of the westbound cavern of Stepney Green finished, just three months after the eastbound cavern was completed.

Crossrail, funded by £14.8 billion from various subsidiaries, including Transport for London and the Greater London Authority, is scheduled to commence train services in 2018. It aims to increase the capacity of London's rail transport by ten per cent and cut the time of journeys across the city.