By Bryn Palmer
BBC Sport in Nepal
Ten minutes before the leader is due home in the world's toughest marathon, a small army of locals are chipping away with axes at the ice on the path metres from the finish.
Yaks on the track; a hazard of the Everest Marathon course
Once that potential hazard is removed, another more awkward obstacle presents itself.
A herd of yaks is inching its way up the same narrow, uneven street in Namche Bazaar, the commercial capital of the Sherpa community in Nepal.
The doughty creatures are unmoved by the kerfuffle surrounding them as they move slowly upwards with their supplies of rice, soybean oil and San Miguel beer.
Welcome to the Everest Marathon, which was run this week (Wednesday) for the 12th time since its inception in 1987.
As well as the world's highest marathon, it can justifiably claim to be the most spectacular.
Starting at 5184m (17,000 ft) above sea level at Gorak Shep, a settlement situated two hours from Everest Base Camp, the route descends to Namche, at 3446m (11,300 ft), before a punishing three-mile loop up to the village of Thamo (3500m) and back to complete the 26.2 miles.
'Descends' is a relative concept, though, since participants have to tackle around 1,000m (3,300 ft) of climbs on the rocky, sometimes icy, mountain paths along the way.
It may be the most stunning start to a marathon anywhere, with a panorama of Himalayan giants stretching from the 7,165m peak of Pumo Ri to the awesome west face of Nuptse (7,861m), with the tip of Mt. Everest poking its head up, peering down on the runners.
But the first mile, notwithstanding the -20C temperatures for the 6.30am start, is brutal.
It includes four uphill sections over the lateral moraine of the Khumbu glacier, a narrow path strewn with boulders, stones and yak dung, every step a potential ankle-twister.
Some would have been happy merely to reach the start in one piece.
As David Beckler, the chief medic at this year's event, says: "The secret to the race is getting to the start line. We don't have many not finish, but quite a few don't start."
The first three winners were all locals
The 70 'Western' competitors, drawn mostly from Britain, with a dozen from New Zealand, a couple of Germans, and lone representatives from Denmark, France and Singapore, all paid £1400 each for the privilege of entering.
In addition 19 Nepalis, many of them Sherpas, compete for the limited prize money - £500, or 60,000 Nepali rupees, to the first male home, £250 to the first female, with decreasing amounts for second and third.
The 'Westerners' arrive in Nepal 17 days before the start to try to acclimatise their bodies to the extraordinary demands of extreme exertion at high altitude.
They walk the same routes and climb some of the same peaks as the thousands of trekkers who flock to one of the world's most exhilarating mountain regions each year.
But inevitably problems ensue, with many suffering forms of stomach and chest ailments common to visitors.
George Dodd, a 65-year-old Irishman, was the oldest original entrant but had to be flown out with a suspected heart condition.
It is the toughest marathon you are ever going to do, and I just wanted to do it once.
But it is not just the elderly who succumb to altitude-related problems.
Louise Murray, a 30-year-old Scot, spends half her year working above 2,000m (6,500 ft) in the French Alps.
But when she started to experience intense pain around her eyes on top of a severe headache in Gokyo, at 4,800m, a week before the race, a traumatic night ensued.
Murray had some classic symptoms of acute mountain sickness, with fluid starting to collect in her brain.
She was given oxygen, steroids, and placed in a portable hyperbaric pressure chamber, also known as a Gamow Bag, where she spent the night with a worried boyfriend Jamie in a sleeping bag alongside her.
Every five minutes a porter would blow more air into the chamber to keep it at the right pressure.
"There was a small window in the bag so I could see Jamie and we could shout at each other through it," Murray recalled. "But it was a pretty miserable experience."
The next morning she was helped down the valley a little way, and made a rapid recovery as her blood oxygen level returned to something approaching normal.
Remarkably she completed the marathon a week later, in under eight hours.
Fellow Scot Angela Mudge, a sports masseuse who lives near Stirling and is a member of the Carnethy Hill Running Club in Edinburgh, had no such problems.
The 37-year-old, originally from Tavistock in Devon, is a world champion in sky running, a form of fell running in mountainous areas such as the Pyrenees and the Dolomites.
She is now the new women's record holder for the Everest Marathon, having covered the course in five hours and three minutes, beating the previous record of former Macclesfield Harrier Anne Stentiford, whose 5 hrs 16 mins had stood since 1997.
"I had absolutely no idea what to expect," Mudge said.
"I race all around the world but have done nothing to compare with this.
Angela Mudge poses at the finish with her medal
"It is the toughest marathon you are ever going to do, and I just wanted to do it once. I always wanted to visit Nepal, and I love using my running to see places."
Mudge finished eighth overall, the first woman home, and the second 'Westerner'.
The first, much to his surprise, was Craig Mattocks, a 34-year-old building surveyor from Northampton, where he is a member of the Wootton Road Runners Club.
"I'm chuffed to bits, I was just hoping for something under six hours," he said, having covered the course in 4 hrs 53 mins to finish fifth.
"I do quite a lot of road running, and did some fell races in preparation for this. But I really just wanted to come to the Himalaya and enjoy the scenery."
Indeed, for the majority of the participants, it is not about times or competition.
The physical and mental challenge is certainly there, but the camaraderie gained from three weeks with a similarly-minded group of people, in the breathtaking scenery of Nepal, is at least as important, if not more so, than the race itself.
John Bull, at 61 the oldest Briton in this year's race, is a case in point.
"I walked all the way", he said after completing the 42 km in a little over nine hours, still three hours faster than the stragglers who arrived in Namche around 6.30pm.
"These guys who do it in four hours or something are crazy - they miss all the scenery!"
The men's record for the event is 3 hrs 50 mins (Haile Gebrselassie's marathon world record is 2:04:26 by way of comparison), set in 2000 by Hari Roka, a three-time winner.
This year Nepalis took the first four places, with the glory going to Lok Bahadur Rokaya, a 27-year-old Nepali who works as an armed police officer in Kathmandu.
He finished in 4 hrs 12 mins, 20 minutes ahead of the second-placed finisher, Karma Rita Sherpa, who hails from Phortse, at the foot of the Khumbu valley.
But the spirit of the event is perhaps best summed up by the lone Singaporean entrant, Steven Wong, who finished in 9 hrs, 15 mins.
The 48-year-old, who has run six marathons - including the Great Wall of China event - since taking up this "crazy sport" three years ago, saw snow for the first time, and suffered badly in the freezing temperatures.
"But I survived, and I am so proud," he said. "I wanted to do something different and for me this is a unique event. It was a once-in-a-lifetime experience."