The guidebook said it was easy. So SONIA WILTSHIRE decided to climb Mount Kinabalu, in Sabah, Malaysian Borneo, the highest mountain in South East Asia. She found getting to the summit was only half the problem...

I'm walking happily, no - elatedly, when it happens. I'm chatting with a lovely Irish chap about us getting to the summit of Mount Kinabalu when I trip and find myself face down on its unforgiving granite.

Six pairs of strong arms appear from nowhere and raise me to my feet in the manner of sailors hoisting a fallen figurehead back onto a ship's bow.

Embarrassment. And pain. Nothing's broken but my knees start to swell and stiffen ominously. A muscle in my arm screams protests. Everything aches.

And I'm 4,000 metres at the top of a mountain and need to be back at its base in a few hours.

Back to the beginning. Ever since I've lived in Wales I've had this thing about climbing mountains. I don't get the chance often, so on my visit to Sabah I was determined to climb Mount Kinabalu.

I hadn't trained as much as I could have because of a leg injury. No problem - Lonely Planet Guide says: 'Mt Kinabalu is one of the easiest mountains in the world to climb...' though it does add, 'all you need is stamina, determination and some weatherproof clothing.'

I can tell you that people much younger than me who got to the top were muttering, as they came down, 'Never again'.

The mountain is part of the magnificent 754 sq m of tropical forest that is Kinabalu National Park, a UNESCO World Heritage Site. At its headquarters, braving a cold wet day more Brecon Beacons than Borneo, we did the paperwork. You are not allowed up there without permits, insurance and a guide. Mine was called Albert, who quite solemnly told me he had a son called Gilbert, who was hired by the marvellous Diethelm Borneo Expedition.

Meanwhile, my travelling companion had opted to stay overnight at one of the park lodges and explore the surrounding walks and forests, like 80% of visitors.

I start the walk at a checkpoint, which sells things like batteries (altitude drains them quicker), rain ponchos, film and chocolate, and begin climbing rocky steps through a landscape of lush forest, full of fantastic wildlife and plants.

It's home to monkeys, goats, numerous species of birds, butterflies and cicadas, rare pitcher plants and indigenous rhododendrons. The original version of our now-garish impatiens plants also grows there.

For Albert, a stocky Malaysian with wispy moustache, wearing improbably delicate-looking pumps on his feet, the climb is a commuter route. He establishes my nationality, marital status and the fact that I don't know the names of all the players in the Premier League and then settles into a companionable silence.

The previous day's climbers had had to turn back because the wet weather made the summit too dangerous so we're not sure that we'll finish the climb .

Despite the rain it's steaming hot. We stop at the 4km rest stop for a quick sandwich. There's a group of buoyant Brits here, who've had to raise £2,500 for charity for the privilege of doing this, followed by a cycle ride, then a spot of whitewater rafting. Later, I wonder how they ever managed all that. We come to a particularly steep, but short, staircase fashioned from granite. 'This is the most difficult bit,' says Albert. 'Good,' I think, 'best to get that over with now.' Turning the corner, there is another one. Then another...you get the picture. For the next two kilometres the misty air gets cooler, the steps steeper and I get wetter as the rain mingles with my sweat.

By six kilometres of this I'm climbing like a drunken sailor, short of breath and weaving slightly. So I'm frankly relieved to see the Laban Rata Resthouse which sits just below the treeline, overshadowed by the brooding, bare mountain and its attendant clouds. At the rest house there's hot food, a tepid shower and the delights of sharing a bunkroom with four pleasant but monosyllabic Dutch people.

I spend five hours utterly awake in my bunk. I'm afraid to sleep, anyway, in case I let down my country and snore. Noise from excited trekkers, and the altitude, mean that no-one else sleeps, either, until it's time to get up at 2am for the trek to the summit.

Groups of us pick our way slowly up the slopes in the dark, head torches making us look like a strange, bobbing tribe of Cyclops making their way to worship the sunrise at the summit. The treeline gives way to sheer, bare rock and sometimes you have to pull yourself up ropes up near-vertical, slippery granite - not so easy when breath is short and limbs tired. Albert saunters up in his plimsolls as if it's a high street. This part is only 2.7kms but it seems like miles in the thin air.

Finally, you get to the last 200m - the even steeper Low's Peak, which needs every last ounce of energy to climb - and where black rats scamper through the rocks in the thin air.

On cue for the euphoric summiteers, the skies lighten and reveal fantastic views, of smaller mountains; villages nestled in foothills and even the sea beyond Kota Kinabalu. 'You good walker,' says Albert, as we head back, and I'm chuffed. I don't think he thought that later.

So the young Irish man (who has a fear of heights) and I are saying we don't think the climb is 'easy' and how his girlfriend had suffered altitude sickness and had had to abandon the climb, when I fall.

At the treeline checkpoint Albert finds a first aid kit and patches me up and I descend awkwardly to the resthouse. I get my stuff, including my walking pole, scrounge a painkiller off a fellow walker, and, by using my walking pole as a sort of pogo stick, make an uncomfortable progress to the bottom of the mountain.

But I made it. Superfit runners, training for the annual Climathon, get to the top and back in around two and a half hours - but that's another story.

And now I'm back home and the aches and pains have gone, my eyes lift to the horizon looking for mountains, and I think, 'well, hey...never say "never again"...'