It sounds like a scene from some dystopian movie - but it's actually a bold new performance event set to take London by storm. It's the brainchild of Hollywood actor and Old Vic Theatre artistic director Kevin Spacey, who was inspired by street artist Banksy's "pop-up" graffiti exhibition in a nearby Waterloo tunnel last summer. In association with experimental theatre company Punchdrunk, he has assembled a crew of performers and big-name urban artists from Antony Micallef to Slinkachu, to create a creepy underground world in the vein of 1920s sci-fi movie Metropolis.