High anxiety at Machu Picchu

Tucked into my state-of-theart sleeping bag in thermal underwear, I'm warm and cosy. But the same can't be said of my travelling companion, GMTV presenter Penny Smith.

It's pitch-black in our rather basic two-man tent and she's currently trying to decide whether to add waterproofs to a sleeping ensemble that already includes thermal underwear, fleece, trousers, socks, hat and gloves.

It's not the first time on our Peruvian adventure that my friend has displayed serious body temperature problems. Neither is it the last.

We arrived in Lima two days earlier along with 65 other supporters of The Children's Society to embark on a sponsored trek on Peru's famous Inca Trail. Our overnight stay was badly timed, as it coincided with the democratically challenged re-election of President Fujimori. Opposition party members were being hosed down with water cannon in the city's main square and there was a blanket ban on alcohol. Lima, we selfishly decided, would have to wait.

The next morning we were bundled, bleary-eyed, into coaches and then on to a plane for the one-hour journey to Cuzco. Once the centre point of the Inca Empire, the city was torn down and rebuilt by the Spanish in the 16th Century. To add insult to injury, much of it was remodelled in the original Inca stonework.

Sipping fresh papaya juice in the sundrenched central square Plaza de Armas, the view confirms that today only the location of the town pays homage to its Inca forefathers. Plaza de Armas is ringed by grandiose Spanish churches. Their soaring spires are impressive, but dwarfed by the magnificent snow-capped peaks of the Andes, wrapped around the town in an inescapable embrace.

Looking at those peaks brought me down to earth. Cuzco lies at 3,360 metres above sea level and after two days acclimatising to the altitude we'd be scaling those mountains. My heart sank. A three-hour stroll along the Sussex cliffs and a gentle ten-mile bicycle ride on Cornwall's Camel Trail were about the extent of my preparation. In 24 hours we would be setting off on a 26-mile vertiginous walk where at one point we would be 4,700 metres above sea level. That's some climb!

We leave behind the charms of Cuzco all too soon. A rickety bus transports us through the 'sacred valley' to the beginning of the trail. Around us the mighty Andean peaks are cloaked in cloud. A good thing, since I'm already filled with trepidation.

The landscape is sheer, and yet covered in lush vegetation. Tiny golden squares of maize grow in spots surely unreachable by mere mortals. 'I love God' is carved into one 90-degree slope in huge letters; on another the words 'Fujimori For President' are etched. In the light of recent events, not so much an appeal as a prophecy!

At Ollantaytambo we meet the porters who will accompany us and carry the bulk of our supplies and tents.

One look at the assembled group of scrawny, pint-sized Peruvians and my confidence soars. If these little guys can do it, surely I won't have a problem. I hadn't realised that their small proportions disguised bodies made of pure muscle.

When they loaded their enormous packs and started jogging up the mountain I was struck dumb.

My day pack, with its litre bottle of water, spare fleece and shorts, camera and a book was already feeling heavy. What on earth had possessed me to go for a hardback!

Thirty minutes into the trail, which begins as a winding path along the Urubamba river and then slowly starts to snake up the mountain, and I am panting for breath. I can also feel the beginnings of a severe headache.

One of our guides takes pity on me and hands me a bunch of his coca leaves. This was no time to be virtuous. When in Rome and all that. I bundle the unappetising handful of dried leaves into my mouth, breaking off a piece of the accompanying revolting lime and ash needed to kick start the chemicals and am soon rocketing up the path, overtaking all and sundry.

This is no great feat since it really does begin as a gentle(ish) stroll. Although one of our party - ironically the hypnotist who in Cuzco had held successful group therapy for 'vertigo' sufferers - is already overcome with altitude sickness (headache, nausea and palpitations) and is forced to give up the climb.

The river gurgles along beside us for much of the day. The one drawback is that it makes me want to pee constantly. As we climb higher the vegetation becomes increasingly sparse and I'm running out of bushes to hide behind.

Walking with so many people means there is always someone nearby. In order to keep track of us all we've been divided into three groups, Blue, Red and Yellow. The first night's campsite for the Reds was in a small meadow by the edge of another mountain stream.

Grubby and caked in dust, I wander down to the water's edge and splash ice-cold water on my scorched face. The sun burns brightly up this high. Next I immerse my aching feet in the stream until they start to lose their feeling. It's not quite a shower, but I've dealt with my extremities at least.

By the time I scramble back up to our tents the rest of the team are slowly meandering into camp. Theirs was obviously a different philosophy which involved taking in the view and chatting to fellow walkers. It was totally incomprehensible to me.

My idea of a good walk is when you beat the previous record time for the distance, don't bother with the view unless it's en passant, munch en route (generally chocolate) and save chatting for the evening campsite. As a result I'd already been nicknamed 'the goat' and as I lapped my fellow walkers I would be greeted by a chorus of bleating noises.

The camaraderie on a trip like this is one of the pleasant surprises. Total strangers, regarding each other warily on the plane journey from London, were by now firm friends. The age range spanned half-a-century, from a 19-year-old lad accompanying his boss to 72-year-old Dorothy, with plenty of stops in between.

Two of the most energetic walk-ers were an Irish-Scottish duo who shared my predilection for coca leaves and earned themselves the nickname 'the coca grannies' as a result. Mairead and Susan met in China on a previous Children's Society trek and became good friends.

Somewhere approaching their 50s (they admitted to grandchildren) they were keen walkers, hilarious companions and kept us up most nights with their chatting and giggling in the next-door tent. Living proof that you're only ever as old as you feel.

Our first night in the great outdoors passes by very amiably; particularly when the supposedly alcohol-free camp suddenly starts flowing with local beer. Graham and John have become the most popular guys around by discovering the spirit of free enterprise alive and kicking in the Andes.

A wooden shack just off the trail houses a family who have set themselves up as an off-licence selling beer, beer or beer. I'm disappointed to find that my wilderness is not as remote as I'd thought, but it doesn't stop me enjoying a few gulps of the local nectar.

By 8.30pm we're tucked up in our sleeping bags in preparation for a 6am start and the most challenging day of the trek. I'm woken next morning by a strange whimpering noise in the tent. Penny has managed to twist herself around during the night, a miracle in itself since with her four layers of clothing she's virtually wedged into her sleeping bag.

Now with the drawstring pulled tight she's woken up facing the back of the hooded bag, to complete darkness and a mouthful of fabric. I look on for a moment in sympathy and then race out of the tent to gather an audience.

As she writhes around like an enormous slug, her contortions go on for a good five minutes before she manages to work herself around and pop her head out of the minute gap she's left herself to breathe through. 'Thanks for the help,' she mutters as we burst into spontaneous applause.

We breakfast on porridge and set off for our marathon climb to Dead Woman's Pass, which at 4,200 metres is the highest point on the Inca Trail. I'm relieved to hear it's named because it looks like a horizontal woman, not because anyone died there. Nevertheless I don't tell Penny, because I don't want her getting complacent.

Although I start out at the rear I manage to bully my way up to be among the first to arrive at the top of the pass.

It's only then that I remember to take in the view! Seeing the dizzying drop to where we began that morning is one of the triumphant moments of the trip. It's also extraordinarily beautiful. From the rocky, tundra-like landscape where we stand littered with wild flowers, we look down the path we've just climbed.

Bright yellow gorse bushes lie scattered like sprinkled gold, wind-battered trees try to stand upright and, far below, the Urubamba River is still just visible. Down the side we're about to descend snakes a series of stone steps created by the Incas which disappear down the valley.

The sparse vegetation slowly transforms itself into tropical cloud forest. Not that I linger too long to take in the view.

I see our next campsite in the far distance and I'm off. Two hours later my knee joints are about to give way when I finally reach camp. It's mid-afternoon and already Pacamayo, the largest campsite on the trail, is filling up with a veritable UN of trekking groups. Some fine-looking Frenchmen to our left, a bunch of excited Americans just below and the handsome Dutchmen that Penny, Mairead and Susan have been cat-fighting over camped just behind the 'facilities'. This Butlin's of the trekking world boasts a flushing toilet and a shower.

I'm beside myself with excitement until I discover that the shower is just a pipe which sticks out of the wall and trickles coronary-inducing cold water on to those brave, desperate or masochistic enough to endure it.

I'm desperate enough and refuse to be put off by the agonised shrieks of the three girls ahead of me. When Penny ambles into camp in time for tea, having spent a pleasant day meandering along making new friends, I'm unable to persuade her to do likewise.

She seems to be embracing the hygienically-challenged part of the trip just a little too enthusiastically. After all, I'm the one who has to share the tent with her.

That night, to celebrate our survival and Graham's birthday, we find two bottles of Peruvian rum on the dining table. At altitude alcohol goes straight to your head and we're soon all plastered.

I've unfairly been dubbed the 'junkie' of the team and accused of corrupting the 'coca grannies', who are now demanding we rename them the more respectful 'coca queens'.

Further down the table a rumour that Blue Camp have got chocolate mousse for dessert has ignited talk of a raiding party.

I wander outside and one look at the mountain sky sobers me up. Layer upon layer of twinkling stars stretching away to infinity and beginning so close I feel I could reach and touch them.

My little corner of the heavens is a sparkling lake shored by the black silhouette of the mountains. I fall asleep to squeals from the neighbouring tent, where Tim is busy wrapping Angie in Bacofoil to stop her getting cold.

It's our last day before Machu Picchu and even the lush beauty of the cloud forest with its gnarled trunks, tangle of vines and delicate orchids, fails to lift my spirits. Every bone in my body aches and the leaden sky is spitting a slow drizzle. Lunch is a sober affair - we're all beginning to feel the strain - and the final two hours before we reach camp seems more like 20.

Penny and I plod in silence, save for the rustle of our waterproofs and the tap of our sticks, individually praying that our tents are around the next corner. When the campsite finally hoves into view it's a dramatic sight. We've been given permission to stay at Intipata; an Inca agricultural site where the whole side of the mountain was terraced to grow crops. Our tents clustered together on the last terrace have never looked more incongruous or more welcoming!

The camp stirs even earlier than usual on our last day. At 5am the groans and moans of my fellow campers as they wake to torrential rain create a hideous cacophony. Or is it the 200 beers bought from baffled staff at the nearby Trekkers Hotel they managed to get through the previous night? Despite the heavy rain, a current of anticipation courses through our ranks.

Two sodden hours later we reach Intipunku (the gateway of the sun) and begin our descent to Machu Picchu. By rights, the world-famous Inca settlement should now be in full view. Instead all we can see is fog.

Then, just as disappointed silence is about to descend, the clouds lift. Like a magician's cloak, they're whisked away to reveal the splendour of the most sacred of Inca sites clustered at the base of the sugarloaf mountain Huayna Picchu.

Aching legs, dirty hair, blisters and bad tempers are forgotten in a second. The sun emerges and transforms the distant snow-covered summits to glistening ice-cream cones, lighting up paths through the forgotten city that beckon us to explore.

This was a moment to treasure for ever. The journey to Machu Picchu is an experience I'll never forget.

Trekking there

The Children's Society will be running a fundraising Peru trek from April 21 to 30. Participants pay a registration fee of £250 (£99 if booked by the start of October) plus £2,250 to cover all travel, accommodation and food, although this can be raised by sponsorship if preferred. For details call 0870 123 4423.