Rail historian, Tim Dunn and Siddy Holloway from the London Transport Museum, get exclusive access to explore South Kentish Town - a station once on the Northern Line, but abandoned more than a century ago. Tube trains still run through it, creating an eerie atmosphere and the spookiest sound they've ever heard in a tube station. They explore the disused passageways, reveal the ventilation shafts still working to keep air circulating on the Northern Line today, and tell the story of the passenger once stranded at the station after getting off a train by mistake.At a secret location somewhere in zone 1, Siddy gets a behind the scenes tour of the London Underground Control Centre . It's the hi-tech mothership of the entire network, sitting in an enormous control room, running operations, power, policing and track access from one central hub. It includes a huge multi-screen display, which can show simultaneous live feeds from any of the 12,000 CCTV cameras on the underground.At the London Transport Museum depot, Tim meets one of the underground's buskers to hear the secrets to her craft - from how you get a pitch to which songs work best at which stations.