The has announced plans to build a new tunnel measuring vmore than 20 miles across . Running between Wimbledon in southwest London and Crayford in the capital's southeast, the project is the latest in a series of works designed to "rewire" south London.

By building deep underground tunnels to carry cabling, the National Grid has said it will keep Londoners connected to "safe and reliable" electricity supplies. At a cost of £1 billion, the project began in spring 2020 and was slated to last seven years. In its latest phase, over 18 miles of tunnels, each 3metres in diameter, will be constructed under the road network between Wimbledon and Crayford, in order to carry high voltage electricity cables. At the moment, most of south London's electricity supply is transmitted through underground cables stored mainly just below the road surface.

When these require maintenance, work is carried out at street level and can be disruptive.

Once the current project is completed, the National Grid says "there will be a number of benefits".

These include "less disruption" as the majority of works will be able to take place deep underground, rather than on the surface.

Future repairs and maintenance work can be carried out "without disrupting traffic, residents and businesses".

It will also be possible to install additional cables in the tunnels to meet future demand.

The National Grid said: "Tunnel construction is well underway, with the project due to be complete and fully operational in 2027. It follows the successful completion of phase 1 in 2018, which was a seven-year, £1 billion programme, building 32km of tunnels and two new substations in North London."

The project is expected to be fully operational in 2026, once all component construction has been completed.

London Power Tunnels Phase 1 began in 2011 and was a similar, seven-year, £1 billion infrastructure project which the National Grid said was "the first major investment in the electricity transmission system in London since the 1960s".

Underground tunnels running to 32km were constructed from Hackney in east London to Willesden in the west, as well as from Kensal Green to Wimbledon in the south.

The National Grid said the project meant the newly built circuits could now carry 20% of the capital's electricity demand and stretched out they would run all the way around the M25.