Episodes airing soon
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Charing Cross
Tim Dunn and Siddy Holloway explore the disused Jubilee line areas of Charing Cross station, now more famous as a film location.
- Not scheduled
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Waterloo and City
Tim Dunn and Siddy Holloway discover the hidden world of the Waterloo and City, the only line entirely underground.
- Not scheduled
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King William Street, Knightsbridge
Tim Dunn and Siddy Holloway explore King William Street, the original terminus of the first electric Tube in the world.
- Not scheduled
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Brompton Road
Tim Dunn and Siddy Holloway walk the Piccadilly line at night to explore the hidden World War 2 remains of Brompton Road.
- Not scheduled
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London Bridge
Tim Dunn and Siddy Holloway explore the disused parts of London Bridge. Siddy visits Ongar in Essex and nearby Blake Hall.
- Not scheduled
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Kings Cross
Tim Dunn and Siddy Holloway explore Kings Cross St Pancras, including a secret siding and the disused Thameslink station.
- Not scheduled
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Elizabeth Line
Tim Dunn and Siddy Holloway explore the brand new Elizabeth Line and have access to two of its stations weeks before the line opens.
- Not scheduled
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Quainton Road and Kingsway
Tim and Siddy visit Quainton Road in Buckinghamshire, 50 miles from London - and once on the underground. Siddy also explores Kingsway tramway tunnel.
- Not scheduled
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Greenwich Power Station
Tim Dunn and Siddy Holloway visit the cathedral-like Greenwich Power Station, which stands ready to power the tube at short notice.
- Not scheduled
Episode guide

Series 1
Secrets of the London Underground
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North End
Tim Dunn and Siddy Holloway visit North End under Hampstead Heath. Abandoned before completion, the station became a Cold War bunker.
Not scheduledNot scheduled -
Piccadilly
Tim Dunn and Siddy Holloway explore the disused parts of Piccadilly Circus, and visit the long-abandoned Highgate surface station.
Not scheduledNot scheduled -
Euston
Tim Dunn and Siddy Holloway explore the hidden parts of Euston, including unique features not found elsewhere and the bits set for demolition for HS2.
Not scheduledNot scheduled

Series 2
Secrets of the London Underground
-
Quainton Road and Kingsway
Tim and Siddy visit Quainton Road in Buckinghamshire, 50 miles from London - and once on the underground. Siddy also explores Kingsway tramway tunnel.
- Not scheduled
-
Elizabeth Line
Tim Dunn and Siddy Holloway explore the brand new Elizabeth Line and have access to two of its stations weeks before the line opens.
- Not scheduled
-
Charing Cross
Tim Dunn and Siddy Holloway explore the disused Jubilee line areas of Charing Cross station, now more famous as a film location.
- Not scheduled
-
Kings Cross
Tim Dunn and Siddy Holloway explore Kings Cross St Pancras, including a secret siding and the disused Thameslink station.
- Not scheduled
-
London Bridge
Tim Dunn and Siddy Holloway explore the disused parts of London Bridge. Siddy visits Ongar in Essex and nearby Blake Hall.
- Not scheduled
-
Brompton Road
Tim Dunn and Siddy Holloway walk the Piccadilly line at night to explore the hidden World War 2 remains of Brompton Road.
- Not scheduled
-
Waterloo and City
Tim Dunn and Siddy Holloway discover the hidden world of the Waterloo and City, the only line entirely underground.
- Not scheduled
-
King William Street, Knightsbridge
Tim Dunn and Siddy Holloway explore King William Street, the original terminus of the first electric Tube in the world.
- Not scheduled
-
Greenwich Power Station
Tim Dunn and Siddy Holloway visit the cathedral-like Greenwich Power Station, which stands ready to power the tube at short notice.
- Not scheduled