All right, I can see you’re not convinced: how can a place called Pottiehill have a dark secret? Yet it does; I have seen it. I have pictures (though some of them are a little odd – an unfamiliar camera).

But first, the curious case of Benjamin Button. (you see what I am doing here? Suspense! The craft of fiction)

Some time ago I pondered the need for an improved gear set-up on my Dream Roadster. In a flurry of energy I actually obtained the necessary 14T cog,

– which is a good deal smaller than the 18T it replaces –

I fitted it (with the usual pantomime of levering off spring clips with screwdrivers and wondering where they will fly to – but at least I had the good sense to wear eye protection)

and set out, only to find, to my chagrin, that somewhere in the few hundred yards I had travelled from the house I had lost the changer button on one side of my Schlumpf Mountain Drive.

I retraced my steps several times, back and forth, but to no avail; so there was nothing for it but to ring Ben Cooper at Kinetics – a splendid shop in Glasgow where I got the Mountain Drive originally, many years ago now – to see if he could supply a replacement. He could, but of course that meant a further delay.

The button comes with its own delicate Allen key, used to secure the tiny grub screw in the centre against the end of the changing rod, where it acts (as far as I can see) rather like a lock-nut.

Though I tightened it vigorously as advised, I am still nervous of losing it again – I wonder if a set of natty leather gaiters (perhaps in matching red) designed to fit the top end of the crank would bring peace of mind? Something to ponder, perhaps even make, in the long winter nights.

In the meantime I obtained another replacement, for my Lucas Mileometer (or Odometer, if you will) which disappeared in the course of my last major excursion – the same one that convinced me my gear set-up needed changing.

But to our tale: it being a fine class of Autumn day for the first of November – All Saints’ Day – I resolved to make an excursion. Not only did I rig the mileometer, I also transferred my ferociusly powerful Smart BL201 headlights (powered by a rechargeable lead-acid battery) from the 1923 Royal Sunbeam. Here we see them blazing futilely against the light of day, ‘crying like a fire in the sun’ as Bob Dylan might say:

Why the lights? Well, if you are off delving into dark secrets, it is wise to have some; I also took a torch, being unsure that I would be able to take my bicycle where I was going. You may notice that I have repositioned my trusty Lidl handlebar bag behind the bars to accommodate the lights, but this proved impractical, as my knees hit against it, so after a short distance on the road I transferred it to the saddlebag position.

I set off over the hill by the Edinburgh Road and down into Strathearn. There had been a heavy shower of rain while I was working on the bike, but the weather was clearing steadily, with sunlight on the distant hills.

In Bridge of Earn I paused to take some pictures, first of a signpost, then of a curious agricultural implement on display near by.

Then off I went along the Wicks o’ Baiglie Road, which once upon a time was the smart route to take if you were driving to Edinburgh and there was a lot of slow-moving traffic ahead:  you knew you would never pass it in the tortuous passage of Glenfarg, but if you belted over the Wicks o’ Baiglie you might well beat it to the other side. These days are gone now, since the M90 motorway now bypasses Glenfarg altogether. But how was my new gear set-up, I hear you cry, plaintively. Very good, I am happy to say, though I did lose my chain very early on ascending the Edinburgh Road; the Mountain Drive in low gear under stress seems susceptible to any variation in chainline. Happily there was no repetition, and I found that I was glad of even my lowest gear ascending the Wicks o’ Baiglie Road, seen here looking back – a long steady mercilessly straight climb:

Earlier, on the flat, I had tried out my Lord-of-Creation one-hundred-and-fifty-inch top gear and found it every bit as delightful as I hoped:  you bowl along at tremendous speed, yet pedalling in a slow and stately manner.  However, I was a little wary of the quantities of wet leaves – a notoriously tricky surface.  At another point there was a constant crepitation as I cycled through beech-mast:  the sounds of Autumn.

The first sign of my destination was the remains of what had been a railway over-bridge looming ahead:

On the other side of it I found a gate which was locked, so I lifted the bike over but was content to duck myself through a large gap in the wire fence, as befitted my years and diminished athleticism.

And there I was, on what was once the North British Railway line from Mawcarse Junction to Bridge of Earn via Glenfarg.  A distant tree caught the sun and blazed out bright gold, which I took to be a happy augury;  there was also a rainbow, and a splendid buzzard which flew up from right to left, which the Romans would doubtless have deemed auspicious.

The line was closed in January 1970, having evaded the Beeching axe, probably because of the proposed route of the M90, mentioned above. It must have been a pleasant one to travel, fairly high up one side of a broad valley at this point, with fine views across to the confluence of Strathearn and Strathtay.

I cycled on through pleasant Autumn woodland, past a great stack of felled timber

And then up ahead, there it was, the dark secret of Pottiehill:

This is the northernmost of two tunnels, each about 500 metres in length, which took the line from Glen Farg across into Strathearn.

I like tunnels. My first serious experience of them was not on the railway (though I have been through many, I am sure, but in a train it is just a darkness) but on the more ancient transport route of the English canals, where there are some splendid and very lengthy tunnels. Transiting a tunnel in a narrowboat is an eerie experience: you are surrounded by dark, with only a narrow horsehoe of light some sixty feet ahead, thrown out by the small bow light, which is not so much for illumination as to let others know you are coming.  The first few times I did it I suffered the consistent hallucination that I was actually in a much vaster space, and not the narrow confines of a tunnel just wide enough to let two boats pass one another and just high enough to give them clear passage.  (My canal tunnel experiences found their way into my writing – in my third published book, City of Desolation, my young hero Jake finds himself on a Dantesque journey through Hell, which has evolved somewhat since Dante’s day, having acquired (among other things) an underground canal system – see here)

The Pottiehill tunnel is a fine feat of engineering and the interior for the most part is dry and entirely sound; the ground is a little uneven, but is not difficult to cycle, though I was glad of my powerful lights, as the tunnel has a considerable bend so that you cannot see the far end and the near one at the same time.

I had heard tales that these tunnels had been used to store old steam locomotives as a precaution against nuclear war (the reasoning being that a steam engine would be easier to fuel than a diesel in the disruption that followed) but I think that is just wishful thinking on the part of old steam men and romantic civil servants.  In this case it would not be terribly practical, since the line has been taken up, and as far as I know, the tunnels (unlike some others) have never actually been closed off.

I emerged from the North tunnel onto a pleasant stretch of overgrown trackbed running between autumn woods, but it was very muddy underwheel and for some distance was in fact the bed of a stream;  but this is the kind of thing that imperial roadsters take in their stride.  I would not attempt it on a narrow-tyred mount.  After some distance I came on a conundrum: the main path rose steeply to the right, with a more overgrown fork descending to the left.

I dismounted and tried the upward path, but had not gone far before reason told me it was much too steep for any railway line. So I turned back, left the bike, and made my way ahead on foot.

The path was not cyclable: it was criss-crossed with fallen trees, and in places was very boggy.

But I persevered and was rewarded with a sight of the North portal of the South tunnel, though it did not look exactly like this:

I went through with the aid of my torch, and again found the surface dry and sound.

There is the rusted shell of a car at the Southern end; I was expecting it, as it is mentioned on various websites; but I still wondered how it got there.

A little way beyond the tunnel, a fine viaduct crosses Glenfarg, and down the side you can glimpse (a good way below) the river Farg and the road running beside it.

I crossed the viaduct and went as far as the gate that bars it; the line runs on invitingly,

while looking back you have a fine view of the South Portal across the viaduct

but for me it was time to turn back. At the South Portal, I came on a strange fellow hanging around:

The South tunnel is straight enough to see both ends from the middle, though you need to stand to one side, so it clearly has a bend in it. I went back through without using the torch, just for the fun of it. It is surprising, once your eyes get used to the dark, just how much you can see, and one thing you notice is how any surface that faces the tunnel mouth behind you catches the light. In honour of my brother Brendan, who instituted a tradition of tunnel-singing on the canals, I tested the acoustic with a verse of the Tantum Ergo. Fortunately there was no-one else to hear.

Emerged on the other side and reunited with my bike (I had chained it to a tree – doubtless an unnecessary precaution, but peace of mind is a great thing)

I made my way back through mud, stream and tunnel,

pausing to snap a harrow sheltering in the North portal, like the remains of some giant insect or alien creature

I think that my attempts to take pictures in the tunnel must have confused the automatic settings, because the shots I took after I emerged had an odd sort of old-fashioned-postcard quality to them,  like this  vista of Strathearn meeting Strathtay.

I saw that there was an alternative route off to the left and hoping to avoid the gate I took it, only to find I had miscalculated somewhat – to my surprise, instead of rejoining the road a little further up the hill than I left it, I found myself swinging right and passing under a substantial bridge that I had not realised was there;  yet I must in fact have crossed it. The reason for it was clearly the stream that I was now cycling alongside, with the road I wanted  on the farther side. However, I was not too perturbed, reasoning that a well-made track must lead somewhere, and it was heading in the right general direction.  A little way on I came on some substantial but derelict farm buildings, which had the haunting quality all such buildings have, enhanced in the picture by the weird colour setting, which nonetheless captures the atmosphere surprisingly well

Carrying on for some way I emerged at last onto a side road; a sign at the point where the track debouched informed me that it was a private road with no vehicular access, so had I come on it at that end, I probably would not have gone up.  As a matter of fact, the way I went is more direct and easier, apart from negotiating the gate, but this was a very pleasant return route.

The light was failing rapidly, not so much from the onset of night as the weather, but as I had neglected to rig a rear light with my headlights, not thinking I would be out so late, I made one more stop for pictures then headed home.

All in all, a most satisfactory excursion and a sovereign specific for driving away melancholy. The route can be seen here.