Sharp was clearly a gifted rock climber, free-climbing a particularly tricky rock cliff rather than rely on iffy ropes. Dougan considered him "definitely the strongest member of our team."
He was a convivial camp companion, who would laugh as other climbers tried to eat their frozen chocolate bars, then pull out his stash of fudge, which remained supple even at high altitudes. He enjoyed his whiskey and beer.
After Sharp made it to the top of Cho Oyu with relative ease, Dougan invited him to join a 2003 expedition to Everest.
They would be climbing the North to Northeast Ridge route -- the one blazed at such great cost by Mallory.
In the high camps, Mallory entertained his team by reading aloud from Hamlet and King Lear. Nearly 79 years later, Sharp carried a volume of Shakespeare in his battered rucksack while making his first assault on Everest.
Most climbers begin their final ascent in the middle of the night so they arrive at the summit in the early to late morning. This allows maximum daylight hours for making the tricky descent and, not incidentally, for victory photographs.
At around midnight on May 22, 2003, Sharp and Dougan left the 8,252m Camp 3 to begin their summit push. Clipping onto a fixed line with metal jumars -- ascending devices that lock onto ropes and attach to a climber's safety harness -- they trudged upward, the spiked crampons on their boots biting into the rock and ice.
Everest's summit has only a third as much oxygen as at sea level. There, climbers are susceptible to frostbite and delirium. Climbers have been known to strip off their clothing in the icy winds, or simply walk off the side of the mountain. Other dangers include fluid in the lungs and high-altitude cerebral edema, or HACE -- a sudden, potentially fatal swelling of the brain.
At about 8,412m, Sharp and Dougan got a vivid reminder of the mountain's dangers.
They had stopped at a limestone alcove littered with spent oxygen bottles. Inside was a perfectly preserved body, the corpse of an Indian climber who had died in 1996. Climbers had dubbed him "Green Boots," for his distinctive footwear. He lay in the fetal position, facing out.
"He looks like he's sleeping," Dougan remarked to Sharp, who nodded.
They continued their climb, and around 8,455m they scaled the first of three nearly vertical rock outcroppings or "steps" that lay between high camp and the summit. As they moved upward, Dougan noticed his friend, normally quicker than average climbers, was slowing down. Just below the Second Step, about 197m from the summit, Sharp removed his oxygen mask.
Dougan noticed that Sharp's cheeks and nose had turned an ashen gray. Sharp acknowledged feeling a funny sensation in his fingers and toes.
"David, this is frostbite," Dougan warned.
The summit was tantalizingly close, just two rock climbs away. But the wind was picking up, and Sharp knew he'd reached his limit.
He encouraged Dougan to go on, but they went down together.
En route, the pair came across a Spanish climber who was struggling upward. They offered the man oxygen and verbal encouragement, and stayed until they were sure he was OK.