The Combe Down Tunnel Anomaly

The Combe Down tunnel was built in 1874, to connect Bath to the Somerset and Dorset Railway. Following the closure of the line in 1966, it remained derelict for the next 47 years, before being reopened as part of The Two Tunnels Greenway, a combined foot and cycle path.

Passing through this tunnel is a strange experience. It is perpetually cold and damp, even on the sunniest of days. It imposes this miserable climate on the approaching path, and you will likely feel cold gusts of wind before you even enter. Once you pass the threshold, natural light is quickly extinguished by the tunnel’s curve, leaving only the occasional wall-lamp to break the gloom. As you continue through wet yellow limestone, supported by intermittent sections of soot-stained engineering brick, you begin to appreciate just how long the tunnel is. At over a mile in length, it is the longest pedestrian tunnel in England.

Inside Combe Down tunnel (Credit: Artur Kozioł)

And then you will hear the music. From about a third of a mile in, wall-mounted disks emit a variety of violin screeches, as part of an abstract musical composition. You might ask yourself, “are these sounds music?”. But there’s a more pertinent question: “What are these sounds hiding?”

During its working life, Combe Down Tunnel was always unpopular with engine crews, not least because it held the dubious distinction being the longest unventilated railway tunnel in Britain. This frequently caused problems, the most serious incident happening in 1929 when the crew of a freight train lost consciousness from the fumes, and crashed into a goods yard further down the line, causing three deaths. But the lack of ventilation wasn’t the only problem. The tunnel was also notorious amongst engine crews for its phantom train noises. Being only a single track line, it was vital to ensure that there was never another train coming in the opposite direction, and so such sounds were never particularly reassuring.

When the tunnel was reopened, these phantom train sounds were heard once again, as before, towards the middle of the tunnel. Even once it had been determined that the tunnel was stable, there was still the problem of avoiding a panic. What if members of the public perceived the rumbles of an approaching “train” as those of a rockfall? And so the musical disks were installed. The atonal violin screeches were a deliberate choice. Although they couldn’t fully mask the phantom noises, members of the public would simply take everything they heard to be part of the same bizarre composition.

The musical disks served their purpose right up until 2016, when the phantom train sounds abruptly stopped. Now they’re simply there to “entertain” those who visit the tunnel.

Despite a wide variety of theories for the phantom train sounds, no one ever came up with a completely satisfactory explanation. While the tunnel was in operation, they were generally attributed to noises from trains further down the line being somehow transmitted along the railway cutting and focussed by the tunnel walls. When the tunnel was being prepared for reopening, a similar theory was adopted, only this time with noises from the Great Western main line being transmitted through a “natural acoustic waveguide” in the geology. Not everyone was convinced, but the terminology seemed appropriately scientific.

However the recently discovered papers of a 19th century Scottish surveyor named Thomas Campbell may finally shed some light on this mystery. Although the lack of ventilation shafts is usually put down to the tunnel’s 300ft depth, it appears that an attempt was made to dig one, only to run into strange problems.

The tale is told in a series of letters back to his family in Edinburgh. The first of these, written shortly after Campbell arrived in Bath, contains the following excerpt:

Contrary to my initial understanding, it seems as if a shaft has already been dug, only to have missed the tunnel below. Therefore my task is not to start from the beginning, but to correct the mistake of a previous surveyor. I have resolved to perform an entirely different series of triangulations from my predecessor, to prevent any chance of me repeating his blunder.

Two weeks later:

I am increasingly baffled by this problem. After completing the survey I found that the position I had calculated agreed with that of my predecessor by less than an inch. I have double checked and triple checked my calculations, but nothing seems amiss. Even if I assume the worst possible imprecision at every stage, multiply each of these deviations by a factor of ten, and assume them to reinforce each other in the worst possible way, I can’t account for the shaft missing the tunnel entirely.

A week later:

I was starting to doubt my own abilities. But then I heard from a work foreman that I was not the second man to survey the tunnel, but the fourth. And we have all reached the same absurd conclusion that the shaft failing to meet with the tunnel is a geometrical impossibility.

The foreman told me of a curious explanation that he had for these problems. It started with a tale told by his grandmother, who was born and raised in the village above. As a young girl, she was walking home when a thick fog suddenly descended and she lost her way. Cold, alone, and terrified, she was eventually found by a kindly old lady, who comforted her and led her back to the village. When her home was in sight, she turned to thank the lady, only to see that she had vanished. The memory had a strange quality to it, in that as the years passed, it grew sharper and more familiar instead of fading. Fairly recently, and exactly fifty years later (this she knew, as it happened to be Saint George’s day) she was walking across Combe Down in very similar conditions, when she found a little girl, lost and afraid, just had she had been. The girl claimed to live in the village, and so she led her back to safety. Just as the houses came into sight, the little girl was nowhere to be seen. She then realised that the face of that woman from fifty years ago was her own.

Asked how his story explained our recent difficulties, the foreman answered “Father Time made a mistake”. It seems he believes that just as his grandmother somehow managed to come to the aid of her past self, so the ventilation shaft has been sunk into the hill as it was half a century ago.

A week later:

This strange notion of Father Time losing his way seems to have spread throughout the men. Some of them recall encountering a void during the construction of the tunnel, which they are now convinced was a fifty year old remnant of the ventilation shaft. Others claim to have heard the rumblings of the trains that are destined to pass through this tunnel, as if time itself has no meaning within this ancient rock. I am almost inclined to believe them.

The letters end there, as Thomas Campbell returned to Edinburgh. He remained a surveyor for another thirty years, but (so far as one can tell) never returned to Combe Down. What happened next is uncertain, but the shaft was presumably filled in and largely forgotten about. (Keeping quiet about such a blunder would certainly have been in the railway company’s reputational interests, particularly in light of the Tay Bridge Disaster a few years later, when botched engineering calculations led to 75 deaths.)

So we now have two instances of related events being separated by exactly fifty years, the first being the tale of the foreman’s grandmother, and the other being the interval between 1966 when real trains stopped passing through the tunnel, and 2016 when the phantom noises ceased. Furthermore, the anomaly seems to operate in both directions. Besides the phantom train sounds propagating both forwards and backwards in time, the foreman’s grandmother was able to interact with her past self, and not just see her. We are therefore dealing with something more than a simple temporal echo.

Anomalous phenomena usually have multiple causes, each one gnawing away at reality, until something eventually gives. Ordinarily, the terror of a lost child would be insufficient to tear the fabric of time. But in a place where the fabric was already wearing thin, a child’s fear just might wear it even thinner. And perhaps the tunnellers, cutting their way through that ancient rock (and no doubt staining it with their own blood on many many occasions) tore the fabric entirely.

Interestingly, the foreman seems to have overlooked one important detail of his grandmother’s story, namely how the fog “suddenly descended” on her younger self. This sudden change in weather suggests that far from the grandmother reaching back in time to meet her past self, the young girl stumbled forwards in time to meet her future self. Perhaps there was nothing wrong with the shaft dug down from Combe Down. The only problem was that there was no tunnel there for it to meet.

I can find no further reports of temporal anomalies in or around the village of Combe Down. Instead, the anomaly seems to have sunk down into the rock. Presumably sound, not being confined to straight lines, can find its way around the edges of the anomaly, thus carrying loud noises both forwards and backwards in time.

So does the central portion of Combe Down exist half a century later than its ends? Is every journey a visit to the future? Maybe so, but don’t get too excited about the wonders (or horrors) that the world of the future holds; they will be on the other side of 300 feet of solid rock.

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