Beneath the streets of Liverpool lies a tunnel network so vast that after 200 years, nobody has found the end of it — and nobody can explain why one man built it.

In the early 1800s, a wealthy tobacco merchant named Joseph Williamson spent his fortune digging tunnels under the Edge Hill district of Liverpool. Tunnels that led nowhere. Chambers with no purpose. A banqueting hall buried underground. He never explained why, and when he died in 1840, the entrances were sealed and the city built over the top.

Excavators have been digging since the 1990s and still haven't reached the edges of the network. Whole sections remain buried under rubble. No complete map exists — and Liverpool is not the only place in Britain where this is true.

This is the story of the tunnels beneath Britain that no one can fully map: who dug them, what's been found inside, and why parts of them may stay sealed forever.

Lost Britain uncovers the forbidden, buried, and forgotten places hidden inside the landmarks you think you know. Subscribe for a new investigation every week.