Just like the chambers of secret in JK Rowlings Harry Potter Hogwart's school of Witchcraft and Wizardry, You won't believe there's a vast Chambers of Secret 100ft under London. It was hand-built to protect thousands of people from terrifying bombing raids by Nazi Germany during the Blitz in the Second World War.
But the existence of the underground shelter beneath Clapham Common remains a complete secret to the vast majority of Londoners, even those who walk above it every day.

