The Prince of Wales and The Duchess of Cornwall visit London’s power tunnels

The Prince of Wales ventured underground today to see a billion-pound project that has future-proofed London's electricity supply for decades.

His Royal Highness descended 16 flights of stairs to see at a network of tunnels carrying huge cables under the capital's streets, while The Duchess of Cornwall stayed on the surface to learn about the National Grid's electricity superhighway scheme.

Wearing a hard hat, high visibility jacket and heavy duty gloves, The Prince walked along a small section of the 20 miles of concrete-lined passages, bored out during the seven-year project.

John Pettigrew, National Grid's Chief Executive, gave His Royal Highness a brief guided tour of some of the tunnels 105ft (32 metres) below the surface.

In a speech at the launch event, held at Highbury sub-station in north London, Mr 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 National Grid has recently flicked the switch to energise more than 124 miles of high voltage electricity cables that carry 20% of the capital's electricity demand - but for The Prince’s  underground tour the power was turned off for safety.

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.

Their Royal Highnesses met staff, stakeholders and local community members during the event and chatted to school children who have visited the National Grid's education centre, set up to encourage young people to learn more about STEM (science, technology, engineering and mathematics) subjects.

To launch the project, The Prince and The Duchess both pressed a button as the song ‘I've Got The Power’ by Snap played from speakers. Their Royal Highnesses then inspected a plaque that commemorated the event.