Shepherd's Bush is a fabulous example of how the network has changed and adapted over time and Siddy Holloway knows where all the best bits are, ready to show Tim Dunn. Just off the platforms the pair discover Victorian glass tiles, long abandoned passenger tunnels from the original Central London Line, epic vents with an eye-level view of people on the platforms and a lift shaft with an escalator through the middle. They visit a gigantic cavern hidden within the body of the station and the perfect example of how nature sometimes beats the best laid engineering plans.

Siddy delves into Elephant and Castle, a small station that packs a big punch. She discovers what it takes to be at the helm of a train from driver Jennifer, reveals the only original 1890 tiles still visible to the public and the spooky discoveries hidden behind a platform door.

At the depot Tim hears about one of the most captivating parts of TFL - the Art on the Underground programme and has the time of his life with Assistant Director Chris Nix as they rev up the special road and rail vehicle currently being restored by the museum.

Tim Dunn and Siddy Holloway have access to the secret spaces of Archway, from cavernous lift shafts to sealed off tunnels. Siddy also visits the tube's own Emergency Service.