Watch Secrets of the London Underground Season 4 Episode 10 Online

Explores the unusual station at Old Street. It serves both the Northern line and mainline trains, and they discover how the platforms and tunnels differ across the two different services. The station has undergone massive changes since it first opened in 1901, and there’s still plenty of evidence of its early years, if you know where to look. Tim goes through a tiny doorway to discover a hidden passage with an original fully-tiled vaulted ceiling. Siddy discovers a staircase last used in the 1920s, which still has the original sign showing the Northern Line tube stops. Siddy visits Hampstead, the deepest station below ground on the entire Underground network. Unsurprisingly, it also has the deepest lift shaft, and she gets to ride on top of the lift to see the record-breaking 55-metre shaft up close. At our Museum depot, Tim meets the first ever female driver on the Victoria line. She talks about working on the tube in the 1970s.