It was the shreds of pinstripe material, held fast in the moraine, that finally brought it home to them: whatever this debris was it had not arrived here recently. Nobody wore pinstripe these days, or at least nobody they knew; not in Santiago to the west of the mountains or Mendoza to the east. Whoever had worn it had done so a long time ago and it was unlikely, looking at the wreckage around them, that they would be in any position to claim ownership. That the ragged pieces of cloth had survived intact was of little surprise. Up here, above 4,500m, the air is so thin and the temperatures so low that decay moves as slowly as the glaciers that etch their way across the mountain sides.

What did surprise the two men was that they should have chanced upon the wreckage like this, after so many years. Whatever else Pablo Reguera and Fernando Garmendia were doing up here, they were certainly not on the hunt for ancient plane wrecks. As the 23-year-old climbers from Tandil in Buenos Aires province would readily have told anybody who asked, this expedition was an attempt to pay tribute to two climbers from their home town who had died trying to climb Mount Tupungato by the same route. A first attempt, on the 10th anniversary of the deaths, had ended in failure. Three years later, they were trying again. Once more it looked like they were destined to fail. There was no shame in that. At 6,800m, Tupungato may not be the highest mountain in the Americas but it is the most challenging. On Tupungato, winds regularly reach 90mph, even in the summer, as air plunges down hard over the summit. When those winds pick up the snow and ice from the upper reaches they blow a blinding white that smothers anything foolish enough to stand in their path. Temperatures drop swiftly to 40 or 50 degrees below zero. It was first conquered in 1897, but since then only half a dozen people a year have made it to the top and far too many have died trying. Part of the challenge lies in its location.

Tupungato sits in an isolated valley close to the border with Chile. Just getting to its base requires an exhausting hike up and over the harsh ridges of a mountain called El Fraile, the Priest. Religious imagery is rife in this region of the Andes, where death comes too easily. If you make it over the Priest's backbone and up the first 4,000m or so of Tupungato itself, you have to contend with los penitentes , brutal towers of spiked ice two or three metres tall that cluster about the summit and which were named for their resemblance to pious, forbidding monks, their heads bowed low beneath sharply peaked cowls. If a god exists at all in these parts, it is a thoroughly vengeful one.

Reguera and Garmendia first approached the summit by following a mountain river, but the penitentes, ever bigger and ever closer together the higher up they went, conspired to block their way. Angry and despondent, they turned back, taking a shortcut down the glacier in the hope that they might be able to find another route to the top. They made camp at the fractured edge of the glacier and the next morning set off again, Reguera leading, Garmendia behind.

They had been walking for only a few minutes when Garmendia called ahead to Reguera and drew his attention to an engine on the ice. Reguera stopped and took off the sunglasses that he always wore against the sharp mountain glare when he was climbing. On the ground next to him, resting on a pedestal of ice, was a chunk of what did indeed look like an engine, if a small one. Inscribed on the side were the words '-OLLS- ROYCE', the first letter of the first word apparently torn away.

Reguera laughed. 'How did they get a car up here?' he said.

It was exactly the kind of poor joke Garmendia expected of his companion. Evidently it belonged to an aircraft, although they had no idea which one - the Andes are as famous for swallowing up aviators as they are for killing mountaineers.

They began to scan the rocky landscape surrounding the lump of engine. Nearby they found pieces of fuselage. There were wing sections, the metal bleached white by the sun and wind, and parts of the plane's electrical wiring system. Soon they were coming across fragments of clothing, including those strips of heavy pinstripe material. They took no photographs and didn't even bother to record the location. In his notebook, under the heading '26 January 1998', Garmendia wrote simply, 'We found a Rolls-Roice engine,' taking so little time over the sentence that he failed to get the correct spelling of the British manufacturer's name.

They didn't for a moment think they had solved one of the greatest aviation mysteries of all time. The find was a mere curio on the way to greater achievements. They had other things to do. They had a mountain to climb.

When he was a child growing up in the 40s, José Moiso and his family lived close to an airbase on the outskirts of the city of Morón, an industrial suburb of Buenos Aires. Often he would stand with his father in their back garden and watch the roaring Douglas DC3s take off and land, and feel the noise of the propellers vibrating in his chest. Sometimes aluminium aircraft passed over, shining and scattering the sunlight, and he would stare upwards as if looking for his own reflection in the burnished metal. To the young José these aircraft were beautiful, thrilling even. It was only later, when his interest in aviation had shifted from childhood wonder to adult obsession, that he would identify them as having been Lancastrians, civilian conversions of the great Lancaster bomber. For now they were just a small boy's object of desire.

To José's parents, the aircraft that rattled the pictures on their walls and so held their son's attention were only trouble. They talked of the crashes that seemed to happen so often in Argentina during the years immediately after the war, and the people killed, especially in the mountains far to the west. That would be a terrible place to crash, up there in the mountains. Surely no one could survive? They talked of one mountain crash in particular. José listened to the story over and over until it became as familiar as the nursery rhymes his parents sang to him before bed. It was the story of the golden plane, a British aircraft that crashed in the Andes loaded down with gold; gold which, if found, promised a life of blissful wealth. But it would never be found, they said, because it had also been carrying German spies from Europe to Argentina. When it crashed, its mere existence had been covered up so that no one could ever find out about the Nazis on board. As to the gold, well, who knew where that was? José, the little boy from Morón, never forgot the story of the golden plane. It would drive his sense of adventure for the rest of his life.

He did eventually become a pilot, though only of private planes. His greater ambition became climbing the mountains that his parents had talked about so ominously. In his twenties he moved to the city of Mendoza, which sits in wine country on the western edge of the dusty Argentine plain, tucked in against the foothills of the Andes. There he became a salesman, trading in electrical equipment, but wherever he was in the city, he needed only to look up and he could see the mountains, by turns black, blue or grey against the clear sky.

In 1974, José Moiso finally combined his two great loves when he flew through the Andes for the first time in a glider, the idiotically light aircraft twisting and turning like a feather caught in a breeze whenever it encountered the sharp updraughts and currents that pressed their way through the stone gullies. The next year, 1975, he climbed to his first wreck: a Douglas DC4, which had crashed 25km from Mendoza on the Cerro Pelado and which had previously been mapped. He came across the fragments of the aircraft scattered across the mountainside at 15,000ft and he quickly found himself engrossed by the fragile relationship that exists in this part of the world between pilots and the jagged earth that lies a worryingly short distance beneath them. He decided to make it his business to search for the wrecks of aircraft lost in the Andes. He believed himself to be the perfect man for the job. People who fly over the mountains never walk in them, he announced, and people who walk in them never fly over them. José understood exactly what it took to do both. Soon his obsession became a family affair when, aged seven, his son Alejo began climbing with him.

To those who asked he would always say that he wanted to find the wrecks so that by mapping them he could pay tribute to the heroism of the pilots. And it was true. He really was interested in the people who had flown in the mountains and died there. But, for all that, he could not get the story of the British plane laden with gold out of his head. Like the metal itself, the tale had a gorgeous allure and it remained with him wherever he was, a motivating force that kept pushing him onward towards each new summit. As the years passed it began to seem as though that was all it would ever be: the unobtainable goal that kept José Moiso in the mountains.

And then, in October 1998, he began to hear a new set of stories: about two young climbers from Tandil who had made a curious find, high up on the slopes of Tupungato.

José was lucky to have heard about the find at all. Pablo Reguera and Fernando Garmendia came down off Tupungato in early February 1998, flushed with success at having finally completed the climb. The first person they saw was the soldier in charge of the mules they had hired from the army mountain station. He all but laughed when they told him about the fragments of aircraft they had found. Why should they suddenly find a wreck if it had been lying there for years? They must have been mistaken.

They were more fortunate with Sergeant Armando Cardozo, who was also up at the station that day. Though the man himself would have denied it - certainly to his commanding officers - climbers who knew him saw Sergeant Cardozo as an andinista first and a soldier second. He had lived in these mountains all his life, had even climbed Tupungato three times. He certainly did not dismiss Reguera and Garmendia's story. He had been around the mountains long enough to know that they could easily turn up the unexpected and unfound. Still, there was not much he could do with the information apart from ask other climbers, as they passed through, whether they had seen anything. None said that they had.

It was many months later that Sergeant Cardozo sat down for lunch with José Moiso, who was visiting the army barracks near the town of Tupungato, a few miles away from the mountain station. José talked about his interest in old plane wrecks. Sergeant Cardozo listened closely. Now he told José about the find that had been reported to him almost nine months before. José was intrigued, particularly by the words etched on to the engine the two climbers had come across: Rolls-Royce was still one of the most famous names in aviation engines.

A few days later, José telephoned Gustavo Marón, a Mendozan lawyer whom he knew had an interest in aviation history. Marón was intrigued, because to his certain knowledge, only three aircraft lost in the Andes had been powered by Rolls-Royce engines. One of those was the most famous Andean plane crash of them all: a Fairchild FH-227, which disappeared in October 1972 after leaving Montevideo, the capital of Uruguay, carrying members of the Old Christians' Club, an amateur rugby team made up of former pupils from one of the country's most prestigious private boys' Catholic schools. The story of how the crash victims survived by eating the bodies of their less fortunate colleagues had become the stuff of legend.

The Fairchild FH-227 had been fitted with two Rolls-Royce engines. But 26 years on, everybody knew where that wreck was. It was part of mountain folklore. Whatever Moiso was looking for it couldn't be that plane. That left two aircraft. One of those was a Canadair CL-44, which also disappeared in 1972 and which had been fitted with four Rolls-Royce Tyne motors. Officially it has never been found but in 1982 two Spanish climbers came across a wheel, two lifejackets and part of a fuselage on the south face of Mount Aconcagua. It was now accepted that those pieces of wreckage belonged to the Canadair.

That left just the one aircraft: a Lancastrian, fitted with four Rolls-Royce Merlins, which disappeared on 2 August 1947. It had been piloted by former bomber pilots from the RAF, had belonged to an airline called British South American Airways and its name was Star Dust . If there really was a Rolls-Royce aircraft engine lying somewhere in the mountains close to Mendoza, it had to belong to the Lancastrian, Marón said. José was overjoyed because he was in no doubt. The Lancastrian was the golden plane that his parents had talked of so often when he was a child.

Much of Pablo Reguera's account was a little odd. When Reguera and José first spoke about the find, Reguera stated emphatically that the engine he saw on Tupungato was a small one, just a few feet across. A small engine would not be powerful enough to get an aircraft to a site 4,500m up a mountainside where it apparently crashed, let alone above the 7,000m needed to clear the Andes. It was probably a confusion, brought on by the low-oxygen atmosphere at altitude. Oxygen deprivation can affect anybody, even an experienced climber like Reguera. Doubt was certainly not a good reason to delay an expedition and time was now of the essence, because soon summer would be at an end and the mountains would become unclimbable.

In January 1999, José went to see Lieutenant-Colonel Ricardo Bustos, commander of the 11th Mountain Regiment. If the Moisos were going to make it to Tupungato in time, they were going to need the army's help. They could supply extra manpower and the pack mules that would be needed to carry all the equipment to the lowest base camp. José had already started talking to Sergeant Cardozo, engaging him in long conversations about viable routes and best approaches and search strategies. For this assault on Tupungato, Cardozo was all but a necessity.

Bustos took some convincing. It would be a complicated expedition, rife with hazards. He would be sending one of his very best mountain men up in search of relics. That said, it was a job to which Sergeant Cardozo was ideally suited. No one knew Tupungato better than him, and it could bring honour upon the regiment. Lieutenant-Colonel Bustos gave the go-ahead. On 10 March 1999, the Moisos began their expedition to Tupungato, together with Sergeant Cardozo, two other soldiers in support and their various pack mules.

It took a day-and-a-half to reach the site they had identified for their base camp, which lay at an altitude of 2,000m. It was tucked in below the formidable - and rarely conquered - south-eastern face. Above them towered another 5,000m of rock and ice where they knew the landscape to be creased and curved in on itself. The team identified three separate segments of the mountainside to explore, each stretching upwards to the summit. For two days they trudged across them, searching for anything on the slopes ahead that might be man-made and yet not part of the debris left behind by climbers. All they found was what everybody else always found on Tupungato: endless rock and ice.

There was just one more segment of the mountain to explore, but it was not to be theirs. At the end of that second day, a ferocious ice storm swept down over the peaks, whipping up the snow from above and cutting off the routes. They would not be going anywhere, either up or down, while the storm was raging. For 36 hours they stayed at base camp sheltering in their two tents, the Moisos and Sergeant Cardozo together in one, the two soldiers in the other, listening to the wind as it blew itself hoarse about them. The moment the storm broke, Sergeant Cardozo said, they should get swiftly off the mountain. Nobody disagreed. Moiso knew full well that their expedition was over, at least for this year.

Seven days after setting off they arrived back at the mountain station, tired and despondent. The expedition had ended in total failure. José could not hide his disappointment. From here on in, as the seasons changed, the weather was only likely to get worse. Tupungato would no longer be merely dangerous, it would become a truly efficient deathtrap. What's more, it would be shaped and changed by the weather. If there was wreckage to be found on Tupungato - and José was convinced it was there - a heavy winter could hide it away for decades. They might just have lost their only real chance of finding the wreck, and José knew it.

That winter was frustrating for the Moisos. Each hint of a blizzard in the mountains sent them rushing for the latest satellite pictures in an attempt to gauge just how deep the snow now lay on the slopes, though it was no substitute for being there. As the year passed, José began to wonder if this was as far as they would ever get. The army, which had seemed genuinely convinced that the Moisos were on to something, now appeared to have lost faith. For many months they claimed not to have the resources to spare, despite constant pleading from the Moisos. Finally, in January 2000, they gave in. José and Cardozo had threatened to attempt the climb without the mules. Clearly the men meant business.

Alejo Moiso studied the map. After the fruit less searching of the first expedition almost a year before, there was just one segment of Tupungato left to explore. It broke down neatly into three separate routes. Of those, one was clearly a harder ascent up tougher rock and ice. It made sense, Alejo said, to do the hardest job first. Sergeant Cardozo agreed. Up here at altitude, their bodies would tire quickly, however fit they were. Better to get the difficult tasks over and done with. At 08.00 on their first full day at base camp, the two men gathered up their climbing equipment and said their farewells to José. On a climb as arduous as this, he would only have held them back and he knew it.

'I wasn't disappointed not to be going,' José said later, when they had come down off the mountain. 'My son is an extension of me. He went in my place.' He knew that without him, the expedition would not have happened; his credit for any discovery was secure and, to José, credit was what mattered.

The two men marched away upwards, stopping occasionally to study the slopes above them through binoculars, but finding nothing. It was 14.00 before they spotted anything at all, and even then it was just a glimmer from the surface of the huge glacier that tumbled down off the peak towards them. Whatever they were looking at, whatever had caught the sunlight, it wasn't ice and it wasn't rock. It was also a fair distance away, perhaps as much as 3,000m. It would take time to get up there and time was now in short supply. It had taken them six hours to get this far, puffing through the thin air, and it would take hours to get back down again. If they left it too late they would be making the descent in darkness, a hazardous venture on any mountain, a potentially lethal one on Tupungato. Spending the night on the mountain was not an option because they were travelling light. They had no tent and no sleeping bags with which to endure the cold. The only refuge was back down with José and the other soldiers at the 2,000m base camp. Alejo and Sergeant Cardozo talked it over, but both of them knew what the decision would be. They had to go on.

'Yes, we took a risk,' Alejo said afterwards. 'We knew that the return would be complicated.' But what is mountaineering without risk? Nothing but a long, hard walk uphill.

It was Alejo who made the first find: a copper oxygen bottle, a little dented but intact for all that, just lying there on the frozen ground at 4,800m. He was euphoric. It had to belong to the Lancastrian. Only an unpressurised aircraft would carry an oxygen tank like this, and the only unpressurised aircraft still missing in the Andes was the Lancastrian. Slowly they began working their way up the slope. Fragments were scattered everywhere, just as Reguera and Garmendia had said they were. Here were small shards of the fuselage and there, embedded in the mountain ice, were pieces of cloth. They pulled at the rags to get them free but all the cloth did was tear and then break down into threads that fluttered away on the mountain breeze. Sergeant Cardozo moved about the moraine picking up the different objects he found, for the most part scraps of the aircraft's metallic shell. He waved them at Alejo and asked him to identify the pieces. Alejo answered as best he could, but he was distracted. What he wanted to find, needed to find even, was anything that could give them positive proof they really were looking at the wreckage of the Star Dust . However hard he looked, he could see nothing like that anywhere.

It was almost 16.30 when they arrived at the site. Together they decided that, whatever happened, they would leave again at 18.00. It was just as they were preparing to turn back that they started finding the pieces of bone. There was no doubt about it. These were human. They continued climbing the slope and then moved up on to a section of the glacier itself, following a trail of bone fragments scattered across the rock and ice. Lying on the surface of the glacier, they found a human torso complete with one arm and hand. It was a creamy shade of calcified white but there was no mistaking what it was: a body that had lain here for a very long time indeed, both exposed to and protected by the elements. Before they could say anything further to each other, Sergeant Cardozo dropped to his knees. There, beside the human remains, he began to pray. The younger man watched him for a moment. Alejo was not religious, but that didn't mean he had to be disrespectful. Slowly, he dropped down on to his knees as well so that he could, as he put it later, 'accompany him in his prayer'.

It was a useful pause. All those years that he and his father searched for the Star Dust there had been one picture fixed in Alejo's mind: a classic plane wreck, complete with lumps of wing and propellers buried in the hard earth and perhaps a little cargo cracked open and scattered about. And, of course, those bars of butter-yellow gold spilling out of their box. Nowhere in those images had there been space for dead bodies. And yet, instead of gold, here was a torso with an arm and a hand. Quietly, his friend continued to offer up his devotion. When he was done, they both stood up and started looking about for other human remains. They soon found them. In all they counted three torsos lying around the glacier plus a single hand, severed at the wrist, the fingers curled upwards as though beckoning to someone. From the size of it, Sergeant Cardozo said, it looked like it had belonged to a woman. Alejo agreed. They left all the remains where they had first seen them and, with the light already beginning to fail, decided the time had finally come to get down the mountain.

Almost 3,000m below, José was surveying the slopes through the fast-falling darkness for any sign of the soldier and his son. It was late, far too late. José knew all too well that the mountain was fractured by crevices; if one of them fell in, the other would struggle to get him out again. In any case, with night coming it would be impossible to mount any kind of search. By morning it would be too late. For hour after hour, José stood outside his tent, staring up at the fading silhouette of the mountain, willing them down.

It was 22.00 by the time Alejo and Sergeant Cardozo made it back to base camp. Night fell, bringing with it a full moon to light their way: a small comfort. Alejo, calmer now after the initial shock of their find, whispered the news to his relieved father. 'I think we've found it,' he said quietly. No, there wasn't any gold, not that they had seen. But there was something else: body parts.

The next day the two men rested. They estimated the wreckage was spread over a wide area up there, possibly as much as two square miles. They needed to make at least one more trip up to the site. José agreed. This time, he said, they should try to find something that would confirm it was the Star Dust .

The following day's climb was much quicker than it had been two days before. Their bodies were better acclimatised to the altitude now and they knew where they were going. It was not long after they had got there that Alejo came across the aircraft's identification plates. This was exactly what he needed. With the registration code printed on them, Gustavo Marón could identify the plane for certain. Alejo slipped them away into his pack. Nearby were a few documents, but when he picked them up to see what they were the paper disintegrated in his hands. The two men separated out and started exploring the mountain side in detail. They came across no more body parts, but there were other relics. There were twisted lumps of aluminium stamped with the British crown and a leather suitcase with the words 'Made in England' embossed near the lock.

A suitcase was a good find, but what José had told his son to look out for was the engine that Reguera and Garmendia had first come across. That was nowhere to be seen. They clambered up on to the slope of the glacier and trudged upwards. Soon the penitentes were rising up around them, becoming larger the further up they went until they were 6m tall. The sun was high overhead now and melting the ice so that lumps of the great pinnacles crashed down about them, shattering as they landed. Beneath their feet they could hear meltwater running off down the mountainside.

'This is a crazy thing,' Sergeant Cardozo said. 'We're actually standing inside the glacier. Let's get out of here.'

'No,' Alejo said. 'I want to stay. Let's just go a little further.'

Unwillingly, Sergeant Cardozo agreed. 'If one of us falls into the crevices up here nothing will get us out,' he said.

Alejo laughed. 'If you fall in you are staying in.'

They moved on until, 700m from the first pieces of wreckage, they finally found the engine, still perched on its pedestal of ice. It carried the words '-OLLS-ROYCE' on the side, just as the two climbers from Tandil had described it. The reason they had thought it was a small engine and therefore a small aircraft was soon obvious. What they were looking at was only a third of the whole. The rest had clearly been cut away, probably in the original crash. Sergeant Cardozo took a photograph of his companion squatting down next to the section of engine, a look of quiet satisfaction on his face. His father had been right. José Moiso's reputation was assured and to Alejo nothing mattered more.

Nearby was something Alejo found extraordinarily familiar: sticking out of the ground was one of the aircraft's four huge propellers, the long, spindle blades intact. In the centre was the cone-shaped hub. As a child, Alejo went often with his father to the Museo Naçional de Aeronautica on the edge of the Jorge Newbery airport in Buenos Aires, where decommissioned aircraft sit on the neatly cropped lawns that look out over the broad River Plate. Among the exhibits is a complete Avro Lincoln, its long, boxy fuselage and double tailfin proof that it was just another version of the original Lancaster bomber design that had made the company's name. Alejo had stared up at the aircraft often enough. It was the same as the ones he had seen as a child. It had to have been made by the British company AV Roe Ltd. That meant only one thing. They really had found the wreck of the Star Dust.