Costain to rebuild London's electricity cable network

London is to get a new electricity superhighway carrying bulk power supplies up to 60 meters underground to replace a network which was created more than 40 years ago.

National Grid today announced that it has awarded a £200 million contract to Costain to bore 33 kilometres of tunnel connecting four of the capital's most important electricity substations.

One tunnel will run from Willesden via St John's Wood to Hackney and the other will come off a spur at Kensal Rise and run to Wimbledon. They will take four years to build and another four years to cable up and turn the power on.

Click the image below to see a graphic of the new network

The new network will handle the massive increase in demand forecast over the next decades including supplying power to Crossrail. The tunnels will be almost twice the height of a man enabling Grid to inspect and repair cables much more efficiently.

Michael Dyke, Grid's UK construction director, said: "Our ambitious tunnelling programme will be built below the existing network, minimising disruption while making sure we continue to deliver a reliable service to millions of people and businesses."

Costain is one of the few companies in the world to have the type of tunnelling machines able to cut through the thick London clay.

Its chief executive Andrew Wyllie said: "This demonstrates Costain's ability to provide cost-effective engineering and technology-led solutions. In addition, Costain also welcomes the opportunity to develop a long-term partnership with National Grid."

Costain shares rose 2½p to 206½p.