Nanga Parbat is the ninth highest mountain in the world. It stands 27,000ft above sea level, its peak towering in forbidding isolation more than 22,000ft above the arid land of the Indus Valley at the western end of the Himalayan range. It is a daunting ascent, imperilled even during the summer months by unstable glaciers, ferocious storms and avalanches. Herman Buhl, the first mountaineer to conquer it, did not reach the summit until 3 July 1953, more than a month after Edmund Hillary and Tenzing Norgay scaled Mount Everest.
Nanga Parbat translates literally as Naked Mountain. It is known to climbers as "The Killer". In the years before Buhl placed his flag at the top, 31 mountaineers lost their lives attempting it. Next year, Reinhold Messner, a 58-year-old German-speaking Tyrolean Italian member of the European Parliament, will set out to climb the peak.
Messner knows the risks. His fame does not rely on his status as an elected representative of the Italian Green Party. He is a legendary mountaineer. The American climber Jon Krakauer has said, "Messner is to climbing what Michael Jordan is to basketball." If you prefer footballing analogies, think David Beckham, Zinedine Zidane and George Best rolled into one. Last month, he was honoured alongside Sir Edmund Hillary during the celebrations to mark 50th anniversary of the conquest of Everest. Crown Prince Paras of Nepal pinned a medal to Messner's chest because, among many stupendous feats at high altitude, Messner was the first man to climb the world's highest mountain without the aid of oxygen.
Messner has climbed Nanga Parbat before. In June 1970, he became the first and only climber to do it via the perilous Rupal Flank. The feat nearly killed him. During the climb Messner lost seven toes and several fingertips to frostbite. He also lost some- thing more precious: his brother Gunther.
On the descent from the summit both brothers were on the brink of total exhaustion and Gunther was suffering obvious symptoms of altitude sickness. They decided to make their way off the mountain via the less steep but uncharted West Face. Reinhold went ahead to scout a route through crevasses that blocked their path. When he turned back to guide Gunther to safety, Reinhold could find no trace of his sibling, only the remnants of a catastrophic avalanche that, after a full day of searching, he concluded must certainly have swept Gunther to his death. In 1971, Reinhold returned to Nangar Parbat to search for his brother's body. He found nothing.
That, at least, is Reinhold Messner's version. And for three decades, as his reputation has grown and his wealth with it, nobody really doubted it. Then, last year, two German climbers, Hans Saler and Max von Kienlin, signed an affidavit questioning whether Gunther Messner ever reached the summit of Nanga Parbat. They went public after Reinhold Messner published a definitive version of the doomed adventure in a book called The Naked Mountain: Brother Death and Loneliness.
In separate books of their own, Saler and Von Kienlin suggest that, far from losing his brother on the way down, Reinhold abandoned him before making the final assault. The implication is that Reinhold Messner pressed on for glory, leaving his exhausted sibling to a lonely and inevitable death. Saler and Von Kienlin were members of the Messner brothers' team during the 1970 climb. They did not accompany Reinhold and Gunther on the final bid for the summit, but they claim that Reinhold's version of events does not correspond with what they witnessed from lower down the mountain. They suggest that Reinhold abandoned his ailing brother to relieve himself of encumbrance and commanded Gunther to make his own way back down the mountain, via their original route and in conditions which rendered it almost impossible. Gunther either died attempting to retrace his steps or froze to death in his tent. If Reinhold's account was accurate, they argue, he would have asked for help in his search from two other climbers he encountered on the mountain that day.
It is an utterly damning allegation. If true it would breach the code of loyalty and mutual support on which mountaineers depend for their lives as well as the human bond between brothers. Reinhold Messner cannot let it stand. He has denied it emphatically. This week, he told the Frankfurter Allgemeine Zeitung that the allegations made by Saler and von Kienlin are part of a "smear campaign". He said: "I will find my brother even if it takes 20 years." Hence the return trip planned for next summer. Messner will use metal detectors in a bid to locate his brother's steel crampons. Finding them could lead him to the body. "If I find my brother where I say he was," he explained, "the whole thing is proved." For further evidence, he has persuaded a friend, the Slovenian mountaineer Tomas Humar, to retrace the route on which Saler and Von Kienlin allege Gunther was abandoned.
Climbers acknowledge Reinhold Messner as the greatest living mountaineer. He has climbed all 14 of the world's tallest peaks without using oxygen and is the author of several books about his sport, including Climbing Without Compromise - the bible of pure alpinism, in which mountaineers reach their target without artificial help or hired porters. There is no doubt that Reinhold was close to his brother. They had shared many difficult ascents in the Alps. If he had not had complete faith in Gunther it seems implausible he would have chosen him as his companion for the most demanding leg of the assault on Nanga Parbat.
Ed Douglas, editor of The Alpine Journal, says: "I don't think anyone will ever know exactly what happened up there. Reinhold Messner was completely strung out. He and his brother had nothing to drink. Their brains were addled by hypoxia. He went back. He found fresh avalanche damage and it clearly devastated him: it was a defining moment. He has described himself as being close to death, on the edge of total collapse. Ultimately you only have the word of the people involved. These allegations have been made before, but I don't think anyone outside the German climbing fraternity would credit the story that Reinhold deliberately abandoned Gunther. The tragedy clearly caused him a lot of pain and it provoked a real rift with his father."
Messner has confirmed that. He once explained: "On Nanga Parbat I understood the reality of my own death. I had not eaten or drunk anything for days. I was hallucinating. My toes were black from frostbite and my brother was lost in the avalanche... My father blamed me for Gunther's death. Gunther and I did so much together. It was difficult for my father to understand what it was like up there."
"What happened would not be unprecedented," says Douglas. People do get left behind. I have found myself separated from a partner. There's a lot of jealousy involved in this."
It is not hard to understand why other mountaineers might resent Messner. Some of his achievements border on the superhuman. His conquest of Everest was achieved entirely solo. In mountaineering parlance, that means that he did it equipped only with boots, crampons and an icepick and without the use of any pre-arranged bivouacs. To add to the machismo of that accomplishment, he made the climb during the monsoon season.
Messner is not a modest man. He has described his own achievements as "sensational" and "unsurpassable". He makes no attempt to disguise the demands of his chosen sport. "High-altitude climbing is about suffering. It is about being afraid. I don't believe anyone who says there's a lot of pleasure in climbing the biggest peaks. It is dangerous, especially if there are no sherpas or fixed ropes and camps. If you make one mistake, you die."
Critics have suggested that if everything he claims to have done was true, Messner would be dead. Fellow mountaineers hint that his brain has been damaged by lengthy exposure to oxygen deprivation. The Pakistani climber Nazir Sabir claims to have smoked hashish with him at high altitude. Others accuse him of "climbing over bodies" to beat fellow climbers to a peak in the Austrian Alps. In 1997, Messner contributed to the legend of his own lunacy by asserting that he had once stood face to face with a yeti in the high reaches of the Himalayas. He claimed it was 7ft tall, immensely strong and agile, with short legs and long, powerful arms. It made hissing noises and he saw its teeth and eyes before it ran into the trees. Messner said he would publish proof, including photographs, in a book about the mythical creature. In the end, he backtracked, arguing that the yeti is, in fact, an unclassified species of brown bear.
Climbing has made him wealthy. Home is a castle, Juval, in the Italian Alps. Each new adventure is followed by a lucrative written account of his bravery. But if jealousy is involved in the allegations about his brother's death, it may be prompted by motives more personal than the excellent living Messner generates by writing and lecturing about his achievements. He had an affair with Max von Kienlin's wife and subsequently married her.
Will his expedition to Nanga Parbat prove his innocence?
"I'm surprised he is going back," says Douglas. "The odds of finding someone who is lost in an avalanche are very low. Sometimes a body is thrown up but, ultimately, you only have the word of the people involved."
Most in the mountaineering fraternity will accept Reinhold Messner's word, even if they believe that his latest attempt on "killer mountain" is motivated by a yearning for adventure rather than any realistic prospect of proving that his brother really did reach the top.