The London Power Tunnels, the capital’s new electricity superhighway, has officially opened under the auspices of Prince Charles and Camilla, Duchess of Cornwall.

The billion-pound revamp of London’s electricity infrastructure lies deep underground and encompasses 32km of tunnels carrying 200km of electricity cables.

The project has been seven years in the making and will help to meet London’s growing demand for power and ensure reliable supplies. It is the most significant addition to London’s electricity system since the 1960s.

The ten new 400kV transmission circuits inside the tunnels will initially carry up to 20 per cent of the capital’s electricity needs and will carry more when older parts of the electricity network, built in the 1950s, are decommissioned. For the royal visitors, the system was switched off for safety reasons.

Charles descended 16 flights of stairs to marvel at a network of tunnels carrying the cables, while Camilla stayed on the surface to learn about the National Grid’s electricity superhighway scheme.

John Pettigrew, National Grid’s chief executive, gave the Prince a brief guided tour of some of the tunnels 32 metres below the surface.

In a speech at the launch event, held at Highbury sub-station in north London, Pettigrew told invited guests: “These tunnels are a huge investment into London’s future, in fact the most significant investment in the capital’s electricity transmission system since the 1960s.

“For decades to come, these tunnels will support London’s growth and its ambition [to] transport power that millions of people rely on in their day to day lives as they work, live and travel in this great city.”

The tunnels, running from Hackney in the east to Willesden in the west, and from Kensal Green to Wimbledon in the south, also house some of the local electricity network company’s cables, saving money and disruption.

To launch the project, the royal couple both pressed a button, as the ’90s rave classic ‘I’ve Got The Power’ by Snap blared out from speakers.

Greg Clark, business and energy secretary said: “The £1bn London Power Tunnels is exactly the type of investment and innovative infrastructure project that the government wants to encourage through our modern industrial strategy.

“This important infrastructure will help increase productivity by cutting the number of road works needed for maintenance, as well as powering London with the safe and reliable electricity supplies it needs for the future.”

National Grid’s decision to place the new cables in tunnels underground helped avoid major disruption on the city’s streets. During construction, workers used electric cars above ground and bicycles in the tunnels below to reduce traffic emissions.