In this first episode, they explore South Kentish Town, a short lived underground station that was reused as a civilian war-time shelter before becoming a ventilation point.

In this episode, Alex Siddy and Chris explore the two halves of Elephant & Castle tube station to uncover the secret disused spaces that lie behind closed doors.

In this episode, the team are given special night access to Finsbury Park to track walk the disused tunnels of the Great Northern and City line; and to discover the ingenious ways in which they were used to upgrade the Piccadilly line during the construction of the Victoria line.

In this episode, the team are handed the keys of Baker Street, which opened on 10 January 1863. They explore the secrets of its 160 years of history, starting from its Metropolitan line origins and the development of the Bakerloo line, all the way to the complex interchange station of today.

In this episode, the team burrow into the history and the hidden spaces of Warren Street, a station with several names and faces.

In this episode, the team explore the history of Marble Arch station and discover some hidden disused spaces - with posters!

In this episode, the team explore Alperton, a Charles Holden station that was originally part of the District line - complete with a hidden wooden escalator!

In this episode, the team head to a classic Leslie Green station that was refurbished in the 1990s before becoming the icon of the Radio 4 panel game - I'm sorry I haven't got a clue.

In this episode, Alex and Chris explore Goodge Street, a station that has changed its name and its appearance and has secret worlds above it and beneath.

In this episode the team visit a very old Underground station dating back to 1868, to explore the many changes to its design and appearance. Along the way they discover a wealth of forgotten spaces, historic features in plain-sight and learn about the latest artwork to be displayed at this stylish station.

In this episode, the team explore the history of Tottenham Court Road station, starting from its humble beginning on the Central London Railway in 1900 all the way to the modern Elizabeth line station of today.

In this week's episode Siddy and Chris explore a Zone 1 station with a history of change and many secret spaces. In the studio the team share a wealth of Collection images and catch up with notes, queries and questions. This is the last episode of the current series before our summer break.