The National Grid has announced a contractor for a £1 billion project to build a 20-mile tunnel underneath south London.

A new network of underground tunnels are to be built beneath south London between Wimbledon and Crayford after a six-year, £400 million contract was awarded this month, which follows planning applications submitted to a number of London boroughs.

Work on the eight-year, £1 billion tunnel project will start in March 2020, with the massive tunnel housing electricity transmission cables 30m underground.

The tunnels will stretch from south-east to south west, with headhouses in Crayford, Eltham, Kidbrooke, New Cross, Lambeth and Wimbledon.

Wimbledon Times:

Up to 63m underground, the tunnels will cross two rivers and 15 train lines with around 200km of high voltage cable.

The new cable tunnels, 32.5km in length, are part of the National Grid's London Power Tunnels 2 project to 'rewire the capital' and improve electricity capacity as demand rises in London.

The National Grid want to replace existing electricity circuits which are coming to an end of their life, and in a major milestone for the project, the Hochtief-Murphy Join Venture will deliver the tunnelling and shaft work for a new electricity cable tunnel south of the Thames.

Existing cabling is now over 50 years old and needs replacing, and the deep tunnel means National Grid can limit the disruption that would be caused by digging up obsolete wiring.

The project was first conceived as a response to increased electricity demand, as well as a way to increase London's access to renewable power from offshore wind farms in the south-east.

National Grid’s UK Executive Director, Nicola Shaw said: “This contract award is a major milestone in the next phase of the London Power Tunnels project and will help ensure the capital has secure, reliable access to electricity to meet the energy demands of the future.”