Ever since it was built in 1912, Woolwich Foot Tunnel has been the subject of rumour and speculation. Running underneath the Thames it connects north and south, and in the hot summer of 1976, when young John Saunders apparently entered the Tunnel and completely disappeared on his way to his sister's house, it was a grim and frightening place. John was never seen again until he re-emerged forty-two years later, complete with an American accent. Happy...