Tube fans would be right in thinking there are 272 Underground stations on the network, but Siddy Holloway has such unique access, today she is taking Tim Dunn to the 273rd. This station only has a west bound platform, no customers and no members of the public will ever board its trains. Situated on the 3rd floor of an unassuming tower block in west London, this is TFL's state of the art training facility. Siddy also heads to one of the oldest and friendliest deep level stations at Oval. She reveals unusual brick lift shafts, surprising ventilation and the international phenomena that started life on a simple station white board. At the depot Tim explores the wild world of experimental and innovative trains and has a mind-blowing experience when he samples hot sauce, homegrown on a tube station platform.

• Sigurbjörg Alma Ingólfsdóttir
• Tim Dunn
• Chris Nix