Prince Charles descended 16 flights of stairs to launch the London Power Tunnels.
The 69-year-old royal went below London's streets to see a small portion of the 20 miles of concrete-lined passages, which have been installed to "future-proof" power supply to the British capital whilst his wife, Duchess Camilla, stayed above ground to learn about the new electricity superhighway.
Prince Charles then returned to the top, where he was joined by his wife as they officially switched on the new electricity.
They both pressed the button to start the electricity flowing and the club classic 'I Got The Power' by SNAP! started playing, shocking the two royals.
Speaking at the launch event held at Highbury sub-station in north London, John Pettigrew, National Grid's chief executive, said: "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."
During the event, the pair also met with staff, stakeholders and members of the local community as well as school children who have been visiting the National Grid's education centre, which has been set up to inspire young people to take more science, technology, engineering and mathematics subjects.
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