Tunnel network under London on Drudge Report
“London possesses one of the world’s most diverse varieties of intricate, hidden and well-used passages, ducts and tubes beneath its streets.”
“While Shrubsole was only able to get access to one part of the tunnel systems, he said there is obviously a much bigger network. “The bits we went into were certainly abandoned, though they still had lighting on when we were in them, so it was being maintained to some extent. There was certainly lots of water dripping off walls and rust everywhere, but the actual deeper level tunnels, I suspect, were being used, otherwise I’m not sure why they would have bricked off access to them.”
http://www.bbc.com/travel/story/20201005-the-uks-rumoured-subterranean-network