The Chancellor of the Exchequer unveiled the newest tunnel under the Thames between Plumstead and North Woolwich as part of Crossrail’s £14.8bn rail link.
George Osborne joined Crossrail staff 15 metres below the river in North Woolwich to celebrate the tunnelling milestone on Friday (June 13).
Two 1,000 tonne tunnel boring machines jointly excavated around 500,000 tonnes of earth under the Thames for the project which will help slash commuters’ journey times from Abbey Wood to central London by up to half.
Speaking from the site the Chancellor said: "As part of our long term economic plan we are investing in infrastructure around the country to create a more balanced, resilient economy.
"Crossrail is not only providing extra speed and capacity for London’s passengers, but also supporting new housing, jobs and businesses."
The high-speed rail link is due to open in 2018 with up to 12 trains running per hour during peak times.
Mayor of London Boris Johnson, added: “London is the engine room of the UK and projects such as Crossrail are helping to drive our country’s economy in the right direction.
"Completion of The Thames Tunnel is yet another important chapter in the Crossrail story - a tale that perfectly highlights how investing in major transport schemes can trigger development and unlock the potential for thousands of new jobs and homes.”
Tunnelling machines Mary and Sophia installed 3,400 concrete rings to line the new tunnels which will soon be fitted out with tracks and communication systems.