While an astonishing 9.2million viewers eagerly tuned in to BBC One on New Year’s Day to see how Sherlock Holmes faked his own death, it was the side story involving the disused “Sumatra Road” tube station that really took Hampstead residents by surprise.
Depicted as an underground launching site for a terrorist network, the show described it as a station commissioned but never opened, constructed but subsequently abandoned.
Seemingly named after a real road running along the railway line in West Hampstead, intrigued residents were left to wonder whether there really could be an abandoned station under their feet.
Although not quite the perfect retreat for an international terrorist group, the show’s writers have revealed the inspiration for their underground lair does exist – but is instead underneath Hampstead Heath.
North End station, which would have appeared on the Northern Line between Hampstead and Golders Green, was built in the early 1900s as part of a line commissioned under the Charing Cross, Euston and Hampstead Railway Act.
Although planned as a passenger station for a new housing development to the north of the Heath, a campaign led by social reformer Henrietta Barnett and a very low projected number of passenger users meant it became the only London Underground station to be built but never opened.
Despite having already constructed staircases, subways and functioning platforms, work was stopped in 1906.
While never used as a launching site for an underground terrorist attack - as is claimed in the show - the Hampstead station’s remarkable true history saw it become a secret Cold War control centre designed to protect London should it be hit with a nuclear bomb.
“In 1939/40, floodgates had been installed at a number of points in tube tunnels near the Thames to prevent water ingress if a bomb penetrated the underwater portion of the tunnel,” explains Peter Kay, railway historian and editor of London Railway Record.
“[During the Cold War] the chosen site for both the emergency control centre and the new floodgate control centre was to be at the uncompleted North End station.
“Work started in spring 1956 at the original station building site in Hampstead Way.”
The quiet, unassuming road running alongside the Heath became the site of one of four underground government “war rooms” in outer London during the height of the Cold War.
Its role as a key defence during the nuclear arms race only ended during the 1980s when risk of nuclear attack subsided and the construction of the Thames Barrier added to London’s flood defences.
Its current life is, as Transport for London (TfL) claims, much less exciting.
Now known as the “Bull and Bush” station – after the nearby pub in North End Way - what looks like a transformer building currently acts as an emergency escape route for tube passengers should a train become stranded.
Access is severely restricted, but one man who did manage to pay a visit - much to the chagrin of officials in charge of the site’s security - was former BBC researcher Hywel Williams.
“I spoke to the right people at the right time and managed to get a pass for the day,” he said.
“You walk down an unusual square staircase - something I imagine must have been a Cold War relic - and come to a long tunnel.
“You can still see tube trains rushing past what used to be platforms, so it can be very dangerous.
“But apart from a solitary toilet and wash basin – which looked still in use - I didn’t get to see much else.
“They wouldn’t allow me to go and see where all the action during the Cold War happened.
“In fact, after my visit I believe there was a blanket ban on people visiting the underground’s disused stations.”
The Sherlock BBC series - starring Hampstead’s own Benedict Cumberbatch - continues tonight at 8.30pm on BBC One.
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