The Hidden Tunnels Beneath London You’re Not Supposed to Know About
There’s a whole other London under your feet… and most people have no idea.
Forget the Tube. Beneath the streets of London lies a shadow city — a maze of secret tunnels, passageways, and long-forgotten networks built for everything from war to espionage to mail delivery.
Some are off-limits. Others have been decommissioned, abandoned, or are officially denied. And a few? You can actually visit — if you know where to look.
Let’s explore London’s hidden underground world, one eerie passage at a time.
1. The Mail Rail: London’s Secret Postal Train
📍 Clerkenwell → Paddington
Built: 1927
Public Access: Yes, via The Postal Museum
Once used to deliver letters without traffic jams, the Mail Rail was a fully automated electric railway operating 70 feet below the city. It ran for over 70 years, transporting millions of letters between sorting offices.
✅ Today, you can actually ride it at the Postal Museum — one of London’s coolest hidden attractions.
2. The Kingsway Telephone Exchange (aka “Q-Whitehall”)
📍 Holborn
Built: 1940s
Public Access: No (classified during the Cold War)
Buried beneath High Holborn is a huge secret bunker, originally designed as a secure telephone exchange during WWII — later repurposed as a Cold War hideout for government officials.
Connected via tunnels to Whitehall and Downing Street, it was once known as “London’s worst-kept secret.” Some believe it's still on standby for emergencies.
Rumour has it there's a bar, dorm rooms, and even a BBC broadcasting studio down there…
3. Churchill’s Secret War Rooms (Now Open!)
📍 Westminster
Built: 1938
Public Access: Yes
Technically not “unknown,” but too iconic to skip — this is where Churchill and his government ran Britain’s WWII strategy.
From map rooms frozen in time to Churchill’s own private bedroom, the Cabinet War Rooms beneath Whitehall are a powerful glimpse into history.
4. The Camden Catacombs
📍 Camden Market
Built: 19th century
Public Access: No (but visible in parts)
These eerie tunnels were once used to house horses and goods for the nearby canal and stables. Today, they’re off-limits to the public — though parts can be spotted behind gates around Camden Market.
Urban explorers have long whispered about their dark, flooded chambers, some claiming supernatural vibes.
5. The BT Tower Tunnels
📍 Fitzrovia
Public Access: Absolutely not (classified)
It’s long been rumoured that a secret tunnel links the BT Tower to key government buildings, acting as a secure communications line in the event of war or attack.
Officially? These tunnels don’t exist.
Unofficially? Even former employees have hinted at their presence.
6. Down Street Station — The Abandoned Tube Stop
📍 Mayfair
Closed: 1932
Public Access: Yes, with London Transport Museum tours
This long-disused station was turned into a WWII bunker for Churchill and his War Cabinet. The walls still carry smoke stains, and wartime maps remain on the platforms.
Book a behind-the-scenes tour through Hidden London — it's creepy, cramped, and unforgettable.
7. The Tunnel Between 10 Downing Street and the MOD
📍 Whitehall
Public Access: No (obviously)
There is strong evidence of a direct underground tunnel between the Prime Minister’s residence and the Ministry of Defence. It’s part of London’s network of classified government tunnels, meant for safe passage during emergencies.
Some former staff even claim there’s a route that leads straight to Buckingham Palace. If true — that’s a seriously royal escape plan.
8. The Clerkenwell Prison Tunnels
📍 Clerkenwell Green
Public Access: No (but some parts visible on private tours)
Beneath the old House of Detention (demolished in the 1890s) lies a web of brick tunnels, once used to move prisoners unseen.
While the prison is gone, the subterranean tunnels remain — and have been used in films like Sherlock Holmes and Spooks.
9. The Victoria Line Test Tunnels
📍 North East London
Built: Early 1960s
Public Access: No
Before the Victoria line was constructed, test tunnels were dug in Tottenham to experiment with boring methods and tunnel linings.
They’re still down there — largely forgotten, but occasionally studied by engineers or historians.
Bonus: Are There Still Unmapped Tunnels in London?
Short answer: Yes.
Long answer: London is built on centuries of layered infrastructure — from Roman roads and plague pits to lost rivers like the Fleet and Tyburn.
There are entire sections of the city where planners still stumble across forgotten passageways, blocked tunnels, or trap doors leading nowhere.
If the walls of London could talk… they’d probably echo.
How to Explore London’s Underground Legally
If this blog has made you want to descend beneath the city, here’s how to do it safely:
Hidden London Tours (London Transport Museum)
Offers access to disused Tube stations like:
Down Street
Aldwych
Charing Cross tunnels
👉 Visit: ltmuseum.co.uk/whats-on/hidden-london
Churchill War Rooms
A brilliant underground museum run by the Imperial War Museums.
👉 Visit: iwm.org.uk/visits/churchill-war-rooms
Final Thought
You think you know London — but half of it is underground.
These hidden tunnels aren’t just relics — they’re stories of survival, secrecy, and strange history.
So next time you're walking above ground… just remember: someone, somewhere, might be walking right beneath you.
📍 Want more hidden London stories? Follow @Londonyaar for secret spots, forgotten history, and the real stories under the surface.