As swathes of commuters dive down into the Highgate underground every day, its elder sibling sits atop - abandoned but rife with nature.

Ham & High: The station was set to be part of the Northern Heights project. Picture: TfL from London Transport Museums collectionThe station was set to be part of the Northern Heights project. Picture: TfL from London Transport Museums collection (Image: TfL from London Transport Museums collection)

Highgate station was built in 1867, opened as part of a steam, suburban rail line from King's Cross and Finsbury Park, allowing people to move out of the squalid conditions of central London and into the leafy suburbs of the capital's north.

In the 1930s a plan was hatched as part of the Northern Heights project to transform the station into a major interchange hub for north London.

The idea was to connect the old suburban railway, electrify it and link it into the northern line, allowing areas such as Alexandra Park and Mill Hill to be better served.

The station would allow passengers to catch trains to Edgware and High Barnet, or into the city to Moorgate and Bank.

Ham & High: A shot from 1972 picturing the station which sits in a cutting on the north side of Archway Road. Picture: TfL from London Transport Museums collectionA shot from 1972 picturing the station which sits in a cutting on the north side of Archway Road. Picture: TfL from London Transport Museums collection (Image: TfL from London Transport Museums collection)

However the Second World War put pay to these grand plans.

Siddy Holloway, London Transport Museum engagement manager, explains: "All of these conversations were started and then World War Two broke out and efforts were refocused elsewhere.

"Once the war was over, the country was hit very bad financially and other priorities had to take precedent such as rebuilding houses and the fixing of vital track and rolling stock."

The Northern Heights project was scrapped, and so too the bold proposals for Highgate station.

Ham & High: The extension of the central line was prioritised above the development of Highgate station and the northern line (photo shot in 1972). Picture: TfL from London Transport Museums collectionThe extension of the central line was prioritised above the development of Highgate station and the northern line (photo shot in 1972). Picture: TfL from London Transport Museums collection (Image: TfL from London Transport Museums collection)

The unification of old railway lines was instead superseded by the extension of the central line.

"This great potential hub of transport for north London unfortunately never came to be," Siddy continued, "and it's said that if the war had only been declared a year later than it actually was, public transport for north London, particularly that area around Alexandra Palace, Muswell Hill and Hanley Gradens, would be served much better.

"You can't really imagine what it would be like today to have such a complicated and extensive northern line, but that is what the plan was."

No longer viewed as a gateway, visionary development, and with the underground station having opened in 1941, the platforms of Highgate station were disused, its tracks lifted and its tunnels partly filled with bricks.

Ham & High: Four tunnels remain, disused: TfL from London Transport Museums collectionFour tunnels remain, disused: TfL from London Transport Museums collection (Image: TfL from London Transport Museums collection)

Yet while the station's closure brought an end to the constant hum of human visitors, its abandonment gave life to a new lease of nature.

In addition to the wild overgrowth that now surrounds the station, its closed off tunnels have become a protected bat habitat for four species including daubenton's, natterer's, brown long-eared and pipistrelle.

Its highest count of bats recorded is 42 and the habitat, which fosters the bats' roosting and holds special 'bat bricks' for them to sleep in, is looked after by Transport for London environment and the London Bat Group.

It acts as a green corridor to aid wildlife moving in and through London, and the abandoned tracks are used as a path for roaming animals and insects.

"Once you abandon a site like that, it's open to the elements and very slowly but surely nature will reclaim it," Siddy said.

"Vegetation started creeping in and then in the 1990s protected bat species were found to have migrated in the tunnels for roosting purposes.

"So this potential hub of activity has now become a sleeping vale of sanctuary for protected animals and species.

"Nature has completely taken over and it's so rare and exciting to witness that, particularly in London.

"It feels like an urban oasis and it's an interesting twist on what could have been."

On the unique character of Highgate station, Siddy added: "It's the fascination of 'what if?'

"It's so interesting to see something that could have made a massive difference in millions of people's lives today derailed by a simple chain of events."

What remains of the site - its four tunnels, platforms, the canopy, waiting rooms and station buildings - can now be explored in person.

The London Transport Museum features Highgate station as part of its series of 'hidden tours', where its unusual and little-known stories are retold.

For more information visit ltmuseum.co.uk.