Parking the car on a lonely road last night as the descending sun slunk beyond the flood plain, I shook the fronds of dust from my old but unused climbing boots. It was 11pm and I was about to climb a mountain.

This isn't the kind of thing I do. For as long as I can remember, my brother and sister have rock- and ice-climbed, cycled, canoed and, most of all, hill-walked their way through weekends and holidays, summer and winter, rain and storm. I, however, didn't get the outdoor genes. I hate exercise and I loathe being cold, away from duvets, hot water and my e-mail. Thus I have never been able to tell my Corbetts from my Grahams - hills of various heights and categories, apparently. Occasionally I would collect my wet, cold siblings from the bottom of misty hills, and regard them, clutching maps and flasks, with a mixture of pity and incredulity. As far as I'm concerned, even mountaineers' car parks should be avoided. They are ripe with one-upmanship and the call to Munro-bag (otherwise known as the aim to climb the 284 Scottish hills of over 3,000 feet). None of this has ever slightly appealed to me.

A couple of months ago, however, my sister, who is otherwise quite sensible, mentioned in passing that she was going out to climb a Munro - at night. I could barely conceal my horror. "But it's fabulous," she said, equally perplexed as to my reaction. "You should come." She went on to outline the advantages of night climbing, especially in high summer - the stars, the mountain to yourself, no midges and no noise. While I planned a bath and early bed with a good book, she planned to have her climbing boots on and to be breathless and sweaty in ascent of Lochnagar. "In fact," she said, looking at me with a mixture of puzzlement and sympathy, "I don't know why you never come." It may have been the fervour in her eyes that got me, or the implication that I was dull and old. Either way, I made my date.

I have never been terribly impressed by Scottish mountains, in the way that a Manhattanite may be left unmoved by skyscrapers. But I found that a mountain at night, specifically a mountain that I was intending to climb, is an entirely different proposition.

So, heading to the north of Glasgow near Loch Lomond, I regarded the quest that was Dumgoyne. One side of it rushes into a cliff edge, sharp in relief against the inky sky. Patchy scree clothes the remaining ascents: but I need not have worried. My nocturnal voyage was under the supervision of my sister and another experienced rock climber, both of whom graciously reassured me that my nausea was not due to altitude sickness (their little joke) or unfitness (it was).

I soon learned the first maxim of night hill-walking: Trust Your Feet. At first, I was frightened. I had no idea where I was going - my eyes struggled to open to the darkness and rocks, and footpaths were indeterminate - but suddenly I got the hang of it. Vision and feet and mountain are in continuous but silent negotiation and once I had stopped thinking about where to walk, my instinct did it for me.

It became pleasurable. Countryside air at dusk has a delicious scent of damp earth, cool and sweet, and with it comes the settling time. Walking towards the hill, through the moist ground, nestling animals called and answered, the noises slightly eerie. A bobbing sea of white-tailed rabbits parted in front of our soft footsteps. Daylight had almost gone. When I stopped for breath - a frequent occurrence - I looked behind me. At first, there was nothing but rugged dark peaks above. But then, flitting into view, were Loch Lomond's luminescent waters, hidden behind hills. Each upward step was rewarded with a deeper night view. Villages snugly pressed between dips of land revealed themselves, sparkling in street lamps, and, just approaching the peak, the whole of Glasgow was suddenly laid out.

The last breath of sunset gave way to night as we reached Dumgoyne's top, and the cloudless sky was studded with stars that winked at and coaxed me through the final few yards.

False summits, I learned, are the bane of the hill-walker's life. My legs were sore and aching, and the first view of the real, hidden peak was demoralising. I felt wretched. Panting and perspiring, the real summit slowly and coyly met my stumbling feet.

The shadowy constellation of surrounding peaks was breathtaking. The final light was yellow and iridescent and the surrounding lochs gleamed. I found myself wondering about the other, distant mountains. I drank my coffee and felt deeply happy. "What's that mountain over there?" I asked, by now slightly recovering. "That's next weekend," I was told. We were now in darkness, but summer darkness, incomplete and hinting at morning. Descending, by now more sure-footed, the air was completely silent. The foothills held the thick density of sleep. This was a stolen, secret, pre-dawn time. I loved it. Mentally, I was rearranging my diary. It seems I've been suppressing my genes.