Secrets of the London Underground

Tim Dunn and Siddy Holloway head to London's iconic Camden Town station - a labyrinthine junction on the Northern Line.

Tim Dunn and Siddy Holloway begin their journey at South Kensington, home of Victoria and Albert Museum, the Science Museum and the Natural History Museum.

Tim Dunn and Siddy Holloway are heading to a stunning station you won't find on modern-day tube maps - Dover Street, now known as Green Park.

Tim Dunn and Siddy Holloway embark on a night-time track walk to the abandoned station of British Museum.

Tube fans would be right in thinking there are 272 Underground stations, but Siddy Holloway has such unique access, she is taking Tim Dunn to the 273rd - West Ashfield.

Tim Dunn and Siddy Holloway are exploring a station in the beating heart of London's theatreland - Leicester Square.

Tim Dunn and Siddy Holloway head to the sprawling Heathrow Airport underground stations - the first ever underground rail link between an airport and a city.

Tim Dunn and Siddy Holloway discover the hidden corners of Shepherd's Bush.

Tim Dunn and Siddy Holloway snoop around TFL's gargantuan maintenance facility - Acton Works.

Tim Dunn and Siddy Holloway explore hidden parts of Archway. Once called Highgate to encourage more people to travel there before an actual Highgate station existed.