Engineers today started digging tunnels for the first major expansion of the Tube network in 20 years.
A giant boring machine is being used to excavate a 3.2km tunnel from Battersea to Kennington, south London, as part of the Northern Line extension.
A second machine will also be employed on the project to extend the Charing Cross branch to Nine Elms and Battersea Power Station.
More than 300,000 tonnes of 'spoil' will be shipped by barge to East Tilbury, Essex, to create new farmland.
The £1.2bn line, expected to become a key commuter route for residents of the power station redevelopment, is due to open in 2020.