Sitting at home, dry and warm and for the first time in almost 36 hours, I re-read the Original Mountain Marathon (OMM) blurb: ‘Held in some of most remote locations and at a time of year when conditions can be extremely challenging, the OMM is meant to be hard.’

Soon after finishing my first OMM, I was asked for three words to define the experience – the experience of slogging for 13 hours across tussock mazes, calf-deep heather and frigid bog, covering some 40 miles while ascending and descending around 3,000 metres. It was too soon to rationally coordinate my thoughts. It is only now that a single word to describe the OMM has crystallised in my mind: chastening.

Originating in the 1960s, the OMM is the Glastonbury of mountain marathons; both are muddy and teem with the unwashed, but unlike the music festival, the OMM moves around Britain, seeking the country’s most challenging mountainous terrain. The destination of the 2015 edition lacked glamour, but the Tweedsmuir Hills in the Scottish Borders are brutish bulwarks of no nonsense.

With the hills bathed in mist and rain skittering across our hoods, Duncan and I began running, immersed in the hopeful optimism that imbues new beginnings. Along with some 2,000 others (all running as pairs), we were carrying everything we needed to survive for two days.

We were very soon moving steeply uphill, with Duncan opening a small yet unbridgeable breach. The pattern was set. The gap grew to a chasm. A reality emerged from misplaced optimism: I was to be tortured; Duncan – aided by a brown and green vastness – would be my torturer.

Faced with a choice of eight categories, we chose the ‘long score’, a course with a fixed completion time of seven hours on day one and six on day two. Numerous checkpoints of different numerical values – far more than we could feasibly visit – were sprawled ominously across a map that we had not seen until the clock had started. There was no route; that was for us to decide. Not only were we our own torturers, we were the potential executioners.

The challenge of the OMM is to override instinct. Think how we like to move over mountains. We follow defined paths; we cross rivers at bridges; we yearn for summits. Our instinct is not to step off the track, not to ignore the highest point, not to slide thigh-deep into a bog. Even in the mountains, humans are not as free as we would like to think. We still crave comfort. The OMM devours comfort, overriding instinct – and, for humans, that can be an uncomfortable experience.

We had been running for two hours. Duncan had already taken the stove, the gas and the tent to lighten the weight of my bag. It made a marginal difference only. I wanted to cry. My legs had been crying almost continually. My body was engulfed in a special brand of tiredness, although I do not know what came first: mental capitulation or physical ruin. The words of the blurb haunted: ‘The OMM is the most complete test of character, determination and is regularly underestimated.’ I just wanted to lie down. Duncan pushed three jelly babies into my palm. ‘They are a bit greasy,’ I moaned. He had put the sweets in the same bag as the cocktail sausages, he confirmed.

Somehow we completed day one, with seven hours of unremitting effort climaxing in a frantic charge downhill on cramping quads to scrape into the overnight camp with minutes to spare. Dinner – soup from a packet, couscous from a packet, hot chocolate from a packet, custard from a packet – was luxurious. I wrapped my feet in gloves, then socks, placed them in the pockets of my waterproof jacket, wrapped a plastic bag over the lot, and then sunk them into my sleeping bag. Seconds later, I needed the toilet.

Day two must have happened because I am writing this article in the past tense, but the memories are hazy – a consequence of the trauma, no doubt. Some things are definite, however, like falling face first into a river, like the sensation of running on ice skates, like the hands-and-knees ascent of an awful hill called Dead for Cauld where the contours clustered like isobars in a hurricane. The ground was always wet, always rough, never level. We did not rest for a moment. By the end, I scarcely had the coordination to descend without fear of stumbling. I had visions of sustaining horrible injuries. I consumed one Mars Bar too many. With time growing increasingly tight, Duncan took my bag. My emasculation was total. Rarely had I endured such type two fun, the sort of activity that is only fun – and I am being generous with this word – in hindsight; frankly, during it is purgatory.

The OMM is about as real as it gets in British running, offering something deeply metaphorical. Here is A, there is B – you choose the way. Make it as hard or as easy as you desire. I cannot say I enjoyed the OMM; I hated it for most of the 13 hours I spent trudging across moor and mountain. But that is not the point. Chastened is good. It is meant to be hard.

@MuirJonny