Constructed in 1940 at the height of the Blitz, the Government was initially against the idea, but public demand grew due to safety fears for millions in London, and Winston Churchill eventually established a labyrinth of secret bunkers below London. The series of eight deep-level air-raid shelters were commissioned beneath Chancery Lane, Belsize Park, Camden Town, Goodge Street, Stockwell, Clapham North, Clapham Common, and Clapham South. However, they were not completed until 1942, so they were initially all used by the Government, but as bombing intensified again, five of them were opened to the public in 1944.
Each shelter consisted of a pair of parallel tunnels sub-divided into two decks with the capacity to hold up to 8,000 people and it was planned that after the war the shelters would be used as part of new express Tube lines paralleling parts of the existing Northern and Central lines.
Ian Stead and his team at IKS Exploration gained access to one of the bunkers, and documented the incredible finds in footage uploaded to YouTube last month.
Mr Stead said: “The London Underground holds many secrets and it’s absolutely brimming with history.
“Construction of eight deep-level shelters started in 1940, seven along the Northern Line and one at Chancery Lane.
“This was in response to public demand for shelter in London Underground stations.
“However, they were not completed until 1942 after the Blitz was over.
“They were initially used by the Government, but as bombing intensified, five of them were opened to the public in 1944.”
The video shows the group exploring various tunnels and rooms of the bunkers, revealing the guard’s stations, toilets and fire escapes.
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He added: “Each shelter could accommodate up to 8,000 people and a pair of parallel tunnels 12,000 streets long lead beneath the streets of London.
“At the time of digging them out, it was thought that they would eventually be used as part of a new express Tube line paralleling the northern and central lines, but that never happened.
“Instead, in 1948, three years after the war had ended, the deep-level shelter in Clapham South became home to 200 immigrants.
“They were the first from the West Indies who came over on the MV Windrush, which was the first post-war ship to bring large groups of immigrants from the West Indies to the UK.
“We’re going to take a look inside one of these disused deep-level shelters that lie abandoned and forgotten.”
The entire documentary, which lasted more than 40 minutes, shows some never seen before areas of the bunkers.
You can watch the full episode on their YouTube channel here.