Season 2

Tim Dunn and Siddy Holloway explore the tube station with the most platforms, Baker Street.

Tim Dunn and Siddy Holloway visit the cathedral-like Greenwich Power Station, which stands ready to power the Tube at short notice.

Tim and Siddy visit Quainton Road in Buckinghamshire, 50 miles from London - and once on the underground. Siddy also explores Kingsway tramway tunnel.

Tim Dunn and Siddy Holloway explore the brand new Elizabeth Line and have access to two of its stations weeks before the line opens.

A secret siding and disused Thameslink platforms at Kings Cross, and disused Marlborough Road on the Metropolitan line. At the depot, Tim looks at a 1904 carriage and discovers the history of the Victoria line's automatic trains.

Tim Dunn and Siddy Holloway explore the disused parts of London Bridge. Siddy visits Ongar in Essex and nearby Blake Hall.

Tim Dunn and Siddy Holloway walk the Piccadilly Line at night to explore the hidden World War II remains of Brompton Road.

Tim and Siddy explore King William Street, the original terminus of the first electric Tube in the world. And the renewal of Knightsbridge Station.

Tim and Siddy discover the hidden world of the Waterloo and City, the only line entirely underground.

As the documentary series returns for a second series, Tim Dunn and Siddy Holloway explore the disused Jubilee line areas of Charing Cross station, now more famous as a film location.