Here's a good one. Our Untold London historian Dan Carrier gets an exclusive first look inside the WWII bomb shelters that British spies later took over and made their base— the bomb proof tunnels said to have inspired James Bond’s Q Branch in Ian Fleming's 007 novels.

People above ground walk by in Holborn without knowing what lies deep below. Soon they open as a major tourist attraction, but Untold London went in first.

In the early 1940s these deep-level tunnels were dug as a vast air-raid shelter. They were later recommissioned as a clandestine base for Churchill’s Special Operations Executive.

For decades staff signed the Official Secrets Act. The complex became the Kingsway Exchange: a self-contained underground world with its own wells, generators, canteen and what was billed as Britain’s deepest licensed bar. In the Cold War a secure hotline between Washington and Moscow ran through here.

Then the doors closed. Until now.

On this Untold London exclusive, Dan Carrier is taken into parts of the network the public has never seen — before the tunnels are transformed into a heritage attraction, intelligence exhibition and the deepest bar in a major city.

If you love hidden London, wartime secrets, spy history and the streets that still won’t give up their stories, this is the one.

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Camera and edit: George O'Rourke

Dan Carrier is a historian and journalist and the author of Untold London: Stories from Time-Trodden Streets.