After six months of training and six weeks of acclimatisation, Rob Hart reached the summit of Everest on May 14. The finance high flier had also lost 15 per cent of his body weight despite all his efforts to eat as much as possible.
The physical exertion of climbing, the brutal cold and high altitude meant he burned through up to 12,000 calories a day, while struggling to consume more than 4,000 calories.
Reaching Everest's 8,848-metre summit was the end of an eight-year challenge that's taken Hart around the world climbing the Seven Summits - the highest peaks in Africa, North America, South America, Oceania, Australia, Europe and Asia.
Acclimatisation is everything when climbing Everest, so all expeditions begin with a trek from the small Nepali town of Lukla to Everest Base Camp at 5,360 metres. The trek takes eight to 12 days, the longer the better for acclimatisation. Tea houses along the route provide a mix of international food to cater for the thousands of people who trek this route each year. Yak sizzlers feature on many menus, but Hart points out that it is unlikely the people of the Solukhumbu district region would kill these shaggy beasts of burden. 'It's far more likely to be water buffalo,' he says.
From Base Camp, trekkers return to Kathmandu while serious mountaineers embark on three sets of 'rotations', a gruelling series of climbs up and down the slopes and perilous ice fields that acclimatise them for a final assault on the summit.
As part of an Alpine Ascents expedition, the first rotation took Hart and climbing guide Michael Horst to Camp 1 at 6,100 metres. After two nights they climbed up another 500 metres to Camp 2 for three nights, before going back to Base Camp to 'fatten up' and recuperate.
Rotations continue for almost a month. During the short Everest season, the Alpine Ascents' expedition cook Ang Tsiring stays at Camp 2 for 40 days to cook for the climbers, guides and Sherpas. All food here is the Nepali staple of dhal bat (lentils and rice). 'At this point it's safer to eat what the Sherpas eat. I ate a lot of dhal bat, three times a day,' Hart says.
Higher up at Camp 3 and Camp 4 the climbers made their own food (from freeze-dried packets) melting snow for water over a stove. 'You force yourself to eat,' Hart says. 'You feel semi-ill all the time and you don't really want to eat. You do want to drink, but probably still not as much as you really need.
'The rotations are important because you lose so much weight at the higher altitudes. Above 8,000 metres - the death zone - you can't really absorb anything and you start wasting away.'
After almost a month of rotations, just after midnight on May 14, Hart and Horst set out from Camp 4 (7,926 metres) in gusting 100km/h winds for the final push for the summit. Even eating power gels - compact concentrated energy drinks favoured by marathon runners and triathletes - was extra tough on summit day as the pair's water had turned to ice. After nine hours of hard climbing with barely a sip of water, Hart and Horst reached the top of the world, and a view that truly deserves to be called awesome.
'One of the biggest ironies of climbing Everest is that when you summit you are at your weakest,' says Hart, who was on the peak for 10 minutes. Four days later he was back at sea level in Singapore with his wife and three young children relishing 'the thick warm air, steak and chips and ice cream'.
Horst descended Everest and immediately climbed up nearby Lhotse, in the process becoming the first person to conquer two 8,000-metre peaks in 24 hours.
Hart and wife Anna actively support the Room to Read charity and have used the expedition to raise money to build schools in Nepal and his native South Africa.
Asked what his next adventure would be, he says 'something more family-friendly', before setting off to hike up The Peak with his two-year-old son.