TBMs were named in honour of the first British astronaut, Helen Sharman, and British aviation pioneer, Amy Johnson

The precision operation required a huge 750-tonne crane to lift TBMs Helen and Amy into the station box in the shadow of London’s iconic Battersea Power Station.

The two TBMs will create two 3.2km underground tunnels to extend the Charing Cross branch of the Northern line from Kennington to Battersea Power Station, via Nine Elms Station.

Joint venture contractors Ferrovial Agroman/Laing O’Rouke expect to complete tunnelling within six months. The extension, targeted for completion in 2020, is the first major Tube line extension since the Jubilee line in the late 1990s.

Both tunnelling machines will now be fully assembled within two 77m long launch tunnels, before starting their journeys towards Kennington next month. When fully assembled, Helen and Amy will each be 100 metres in length.

After both tunnel boring machines and their gantries are constructed, a conveyor system will be built to take the spoil from the tunnels up to barges on the River Thames.

More than 300,000 tonnes of earth will be excavated by Helen and Amy in this way before the spoil is taken to Goshems Farm in East Tilbury, Essex by boat where it will be used to create arable farmland.