[3][4] Secrets of the London Underground was first broadcast in the United Kingdom from 19 July 2021 on Yesterday.

The series explores hidden areas of the London Underground such as abandoned tunnels, secret bunkers and hidden staircases, and delves into the archives of the London Transport Museum's Acton Depot.

[5][6] The format of the programme generally centres around visiting two abandoned areas of the London Underground, in addition to viewing some of the Museum's collection at Acton, usually with assistant director and 'Hidden London' co-developer Chris Nix.

Jacqueline Hewer, CEO of the programme's production company, stated "We can promise one thing - you'll never travel on the tube again without wondering what's through that door at the end of the platform..." UKTV's Hilary Rosen, deputy director of commissioning, described the series as "Viewers are fascinated by the Tube and this series promises unseen locations, fresh stories and secrets galore from right across the city.

[12] A fourth series of ten episodes was commissioned in February 2024 and broadcast between July and September 2024.