Clambering almost vertically, with a wall of mountain before my eyes, I found the air growing thinner and breathing ever more difficult. Above, the piercing blue sky seemed to extract the oxygen from the mountains beneath. Even the fleet-footed porters looked anxiously over-stretched as they ran past. Conrad, a member of our party, had fallen into step alongside me. As if on some superhuman mission, we calculated every movement forward, 10 or 15 steps and then a pause.
"Please don't think you have to wait for me," I wheezed, my asthma for the first time a problem in our hike towards Machu Picchu, the legendary site of the Incas. "Don't worry," he said, in short snatches of reply. "You may notice ... that I have to pause ... as frequently as you do."
Our climb upwards had not been too tough at first. The worst of altitude sickness was past; our party had already spent a fortnight acclimatising as we travelled Peru in a giant truck. And the first day of our 24-mile walk had been a moderate affair, to get us into the swing. Cactus vied with snow-topped mountains in the most spectacular of scenic views. Below us, as we walked one behind the other through the lower stretches of the Andes, a turquoise river flounced through the valley floor, tumbling round the boulders.
Our first night in tents, erected for us by our porters, had been cold - though not the coldest we endured. Not like the night at Chivay earlier in the holiday, where the water froze in our water bottles and the tents were stiff with ice by morning. At Chivay, even a sleeping-bag designed for temperatures down to minus 10 seemed little more protection than a sheet. And the truck refused to start next morning. Early winter in Peru makes for clear, warm, sunny days, but bitter nights.
Here on the Inca trail, life seemed less demanding at first. But after our easy introduction, this, the second day of climbing upwards, was much much tougher. We set off all together, but the steepness of the journey, up through woods, mountain pastures and on to Dead Woman's Pass at nearly 14,000ft, soon separated us.
Mark and Liz, our truck-driving tour leaders, leapt on ahead, Monica and Abigail close behind them, but, finding it tough, the rest of us straggled onwards at whatever pace we found tolerable.
Reaching the top, I staggered to the edge, refusing to join the first arrivals sitting waiting until I knew I had no farther to climb. The sight was astounding: miles of steep mountains, verdant with rainforest with all the appearance of a virgin land from a past age. Conrad and I posed for congratulatory photographs. There was a real sense of achievement. Eventually, all safely reunited, we descended to where the porters had prepared lunch.
Sitting at our picnic tables on tiny, collapsible picnic stools, in our stout walking boots, we must have resembled one of the more eccentric English dining societies. In three-and-a-half days climbing through the Andes we had some spectacular meal-times, but possibly nothing as astounding as the panorama below the pass.
Our journey continued up and down original stone steps, some knee-height in depth, where the Inca messengers once ran from the distant city of Cuzco. By the fourth morning, we were nearly at Machupicchu. Rising in pitch blackness at 4am, we dressed, clumsy in the confines of our tents, and set out by torchlight. As the first, grey-pink streaks of dawn illuminated our progress, we arrived at the Sun Gate and the vast city lay below us.
Known only to the local Peruvians for three centuries, Machu Picchu was revealed to the West in 1911 by an American archaeologist, Hiram Bingham, who was looking for the lost city of the Incas. The 15th- and 16th-century ruins of temples and palaces, threatened last year by forest fires which made the site impassable for some weeks, are a United Nations heritage site perched at nearly 9,000ft.
For all our party, a mixed bag of mainly professionals in our thirties, with a young Oxford graduate and a retired chemical engineer at either end of the age spectrum, Machu Picchu was the highlight.
Over three weeks, we had explored the coast and the desert before travelling to the high inland plains. Sometimes we camped and cooked for ourselves with food from local markets; then, just when we thought we could not take another freezing night, a hotel would provide a touch of luxury.
At Nazca we had hired tiny four-seater planes to fly us over the mysterious lines, shapes of birds and creatures inscribed across the desert centuries before when flight was unknown, yet almost impossible to see at ground level. In the Colca Canyon, Peru's answer to the Grand, condors had soared above us. On Lake Titicaca we sailed in silence on boats of reed.
Yet the walk to Machu Picchu triumphed because it made us feel like explorers. In recent years, visitors had made the trail filthy with waste, but the route has been cleaned up and our tour leaders rigorously enforced the no-litter rule, so all around was only nature. The site is out of bounds to coach parties, because there is no road and you can arrive only on foot or by train.
Ours was an affable group of people, large enough to dilute the irritations that emerge in any organised group, small enough to maintain the sense of adventure. We had already formed friendships while jolting our way through Peru by truck. Nearly all of us walked the Inca trail. It was the kind of experience you call "bonding".
Louise Jury travelled with Exodus, 9 Weir Road, London SW12 0LT (0181- 675 5550). She paid pounds 1,460, which included travel and accommodation for three weeks.
For independent travellers, there are plenty of bargain air fares to Peru at present. For example, Iberia (0171-830 0011) is offering a fare of pounds 533.50 from London or Manchester to Lima.
I met a traveller in a London pub who had been to Central America and India, and was planning to tour Cambodia. He took a dim view of sanitised package holidays and organised tours to far-flung places, and a similarly dim view of people who go on them. We argued, and at the end of the evening he punched me several times in the head and stormed out of the pub.
I believe that people go on different holidays for different reasons, and they are entitled to do what makes them happiest. After all, that is what being on holiday is meant to be about. But I found myself in a dilemma on returning from an organised tour of Peru. As an independent traveller you choose your company and where you go, and you take pleasure in resolving the numerous daily mysteries and hitches that confront you. When you are part of a tightly planned tour, you cannot choose your companions and you find that someone else has already been paid to resolve all those daily mysteries and hitches on your behalf. And even if you are open-minded you find that you have prejudices after all, though not so strong that you are driven to beating a stranger into the ground.
Our tour was run like a military campaign from start to finish. There were briefings and debriefings, dressings-up and dressings-down, and tardiness was a punishable offence. The leader had a curious way of barking instructions and ignoring group members' attempts to talk to him. He could not conceal his contempt for the locals, whom he described as savages. And his dislike for the people he was leading became apparent when he announced that he would gladly exchange two of the party for a "charming couple from Weybridge" whom he'd met along the Inca Trail.
Rumours spread like the wings of hungry condors. One female member of the party alleged that the leader had propositioned her in her hotel room on the first night. The following morning he was purported to say that complaining would be useless because "we are all old boys together back in England". A young Cusquenian guide, stumbling miserably over her words, said the leader had told her that her mother was uglier than a mummy in the Gold Museum in Lima. The lowest point of the tour, and perhaps the defining moment, was a visit to the Yagua Indians' village on the banks of the Yanacuna river. With advance warning of our arrival, they had dusted off their traditional costumes and strung out a motley collection of factory- produced tourist artefacts on a makeshift washing-line. The women wore authentic straw garments over their shoulders, but the illusion was hopelessly dashed when one of them turned around and grinned, revealing a prominent bikini-line across her back and a mouth full of extensively crowned gold teeth. The chief of the tribe then gave a demonstration of his blowpipe during which he missed the target - a 2ft wide banana tree - four out of five times.
When asked how he managed to hunt, he explained that he preferred to blow monkeys out of the trees with a shotgun. Despite our reservations about poking around a traditional hut, we were urged to do so to witness the Yagua Indians' unchanged way of life. In this way we were also obliged to give them a tip of two sols on the way out. That is a lot of sols from a group of 10 people. As we walked away from the village, a radio whined out strains of Sheena Easton's "My Baby Works from Nine to Five", and I noticed a pair of brilliant white Nike trainers on someone's doorstep.
So perhaps you can appreciate my dilemma. There I was, clinging on to the moral high ground in a pub in central London, only to find that I am an embittered old hypocrite after all. I think I'll go to Antarctica on a shoestring next year and really punish myself.