The railway is all but invisible. Burrowed beneath the steep slope of Bristol’s Avon Gorge, even its two entrances are relatively hidden. On the hilltop, the railway’s shiny new sign is overshadowed by the Victorian-era Avon Gorge Hotel; at the bottom, the tunnel spits out onto a freeway where few pedestrians would stop to notice the worn stone entrance.

As a result, only in-the-know locals tend to realise there is a tunnel here at all – never mind why it’s special.

This hidden tunnel was home to a rare underground railway – which later served as both a World War Two bomb shelter and as a secret transmission centre for the BBC. What started as quaint transport built for a Victorian spa turned into something much more grim.

Over the last 12 years, a group of volunteers has been working to change that. It’s unlikely they’ll ever return the railway to running order. But by restoring parts of the tunnel and opening it for visitors, they are hoping, at least, to shed light (quite literally) on this part of Britain’s history. And not just on the engineering feats of the Victorian era. “The wartime story is as important as the railroad story,” says Maggie Shapland of the Clifton Rocks Railway Trust, the volunteer group restoring the tunnel.

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Even so, the story of the railroad – which remains the only four track cliff, or “funicular”, railway in the world – is a strange one.

In the late 1800s, Clifton, at the time a separate town from Bristol, was an upmarket area of Georgian terraced houses. The area along the river below, however, was a port busy with sailors and other tradespeople. There was no easy, efficient way for those at the bottom to make the trek up to the top.

Many of those in Clifton preferred it that way. But entrepreneur George Newnes had other ideas. A publisher best known for The Strand Magazine, the first home of the Sherlock Holmes stories, he knew that connecting the two areas might not be something the well-heeled residents of Clifton would want – but that it could be a money-maker. Just a few decades earlier, Clifton had been a destination for spa-goers. If he built a new spa at the top of the gorge and a transport link between the baths and the port, Newnes could profit off of the revived tourism… and so could Clifton.

The town gave Newnes permission to build the railway, but with caveats. To avoid spoiling the gorge views, the transport had to be in a tunnel. No alcohol could be served. And to keep hotel guests separate from ‘the common man’ who would be taking the railroad, the tunnel’s entrances and exits had to be kept separate from the garden of the Victorian hotel next door, says Shapland, who is writing a book on the history of the railway.

Getting permission was only the beginning. Engineers originally thought the tunnel, which was 500ft (150m) long tunnel and ran 230ft (70m) deep, would take only a year to dig. They quickly had to re-assess. Thanks to the number of rock falls caused by digging the tunnel – which had a 45% gradient – through the fault-riddled limestone, engineers decided that the tunnel needed to be lined with brick.

The construction was laborious. The limestone cliff was blasted with a tunnel of 27.5ft (8.2m), making it the widest tunnel of its type in Britain. It was then scaffolded with timber struts and lined with a 2ft (0.5m) brick wall. The work required such specialised skills that men had to be brought all the way from Canada to do it.

Even so, the process remained accident-prone: one rock fall just six weeks before the tunnel was finished barely missed a horse tram passing below.

When the railroad opened in 1893, the work seemed to have paid off. More than 6,000 people made a round-trip journey between the bottom and top of the gorge; over the following year, the railway saw 427,492 passengers.

The new bathhouse at the top of the hill, which, according to Shapland, Newnes outfitted with all of the latest amenities to make it “the biggest and the best in Britain”, was part of the allure. But so was the railway itself. As a funicular railway, as one car went up the tunnel, it was balanced by a car on the other side, attached via cable, which went down. Huge water tanks made the descending car heavy enough to be able to pull up the ascending car. The conductor of the car at the bottom used an electric telegraph – at the time an extremely modern gizmo – to tell workers at the top how many passengers he had and, therefore, how much water had to be added to the opposite car.

Sharp decline

As impressive as this type of engineering was for the time, it wasn’t enough to keep passengers coming back. By the 1920s, the railway was losing £1,000 a year. People were starting to drive with their own vehicles, and because people didn’t live in the port area at the bottom, there wasn’t commuter traffic. The rail cars took their last journey in 1934.

Then came World War Two.

“You’ve got a tunnel not being used – and everyone wants to go underground,” Shapland says.

That was particularly true in Bristol. The fifth most bombed city in all of Britain during the war, it was a target for two reasons. First, it was the home of both a busy harbour and of the Bristol Aeroplane Company, which produced some of Britain’s most important fighter aircraft. Second, both its iconic bridge and the River Avon made it easy to spot. During the Blitz from November 1940 to April 1941, 77 air raids killed 1,299 people and destroying more than 80,000 houses in the city.

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The upper part of the tunnel was re-opened to residents escaping the bombs. The lower part was requisitioned by the BBC, which decided to use it to re-house the BBC Symphony Orchestra when they evacuated from London.

“At first we had rented the Clifton Spa Hotel and the ballroom to accommodate them, but to our horror, and just before they arrived, Imperial Airways requisitioned the whole hotel over our heads,” Gerald Daly, the engineer in charge of the BBC West region at the time, wrote in a letter recounting the events. Ultimately, the BBC settled on the old railway tunnel – where, after 60 musicians played underground, it was found that as well as providing safety the tunnels provided a musical quality that “was better than expected".

As bombings increased, the Symphony Orchestra moved to Bedford. But the BBC still needed an alternate broadcast centre for some of its London staff. If communications were cut in London – which seemed not unlikely, given the beating the city was taking – there needed to be a backup to broadcast to the public and keep up morale. Not only that, but there were radio broadcasters based in Bristol who needed a safer venue to work.

They decided to re-design the tunnels to make them into studios. The complex was dubbed the Tunnel Fortress.

The ‘fortress’, which sat under more than 50ft (15m) of solid rock, was at the lower end of the tunnels, separated via a locked and sealed door form the public air-raid shelters. It included a transmitter room, which would stay in communication with all of the other BBC stations in case telephone links went down; a recording room; a main control room that transmitted programmes in 40 different languages; and a canteen. After six months of work to build the complex, the team moved in in 1941.

“For the rest of the war, this was the nerve centre of the BBC in the west of England,” Daly writes. “All programmes of the BBC to home and overseas passed through the Tunnel control room for the next four years.”

At the time the tunnel was being re-designed, it was thought that, if London fell, the tunnel would be the last location of the BBC. Daly writes that his mother-in-law sometimes had dinner with none other than Winston Churchill during the war. She once asked him if, in the worst-case scenario, he would take the heads of the BBC with him if he fled to Canada. “What use would they be there?” he reportedly answered. “Let them make a last stand in their Bristol Tunnel – it’s the best place for a last stand that I know of!”.

None of that would be necessary. Just as the workers got settled, air raids on Bristol all but ceased.

The BBC remained through the first phases of the Cold War when it was thought to be a useful back-up base in case of Soviet attack. Finally abandoned in 1960, the tunnel was allowed to go derelict.

Today, open to the public on either ‘open days’ or by pre-booking, the tunnels have entered yet another stage. They are eerie and empty. Entering the ticket hall – which still has a rusty turnstile – and descending into the tunnels themselves is like a walk through a terrestrial Titanic. Water drips down the brick-lined walls. When the electric lights are switched off, we’re plunged into complete blackness.

Opening the tunnels back up has been a painstaking effort which has required clearing tonnes of rubble, installing lights, building an exhibition and arranging regular guided visits (over the last year, the volunteers have led 86 tours). In the first air raid shelter alone, Shapland says, they took out six skips of just broken bottles.

A great deal of work remains. Rocks, debris and even the splintered remnants of furniture remain piled in the BBC rooms. The constant dripping of water into the tunnels is an ongoing problem. With everything done on a volunteer basis, the work of restoring and maintaining the site can be stop and start.

But even, or perhaps especially, in the stage they are now, the tunnels are an eerie reminder of a bygone time. A sign titled “Regulations for the Use of Air-Raid Shelters” remains tacked against the wall, reminding people that they must leave both their children’s cots and any pets behind. Since people would return to the same place in the shelter again and again, they tended to leave belongings in place. As a result, pairs of dusty children’s shoes line the display cases in the small exhibition area. Volunteers even found a tea kettle in the BBC canteen.

The most poignant remnant of all, however, may not be from WWII at all. At the bottom of the tunnel, at the river-side ticket hall, someone has pencilled graffiti on the wall. One sketch is of a curvaceous beauty. Another is an early version of Mickey Mouse, with the trademark large, black eyes he had in the 1930s. Maybe the artist was one of the last people to take the railway before it closed. More likely, it was someone leaving his mark in the years between when the train closed and WWII began. Back then, it would have been difficult to foresee how the derelict railway – once a Victorian marvel of engineering – would be re-purposed for some of Britain’s darkest days.

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