Now around 400 runners attempt the challenge each year, with a finish rate of between 60 and 83 per cent.
It's one of four 100-milers in the US, including the Leadville 100, aka the "Race in the Sky", which begins at an altitude of 3,100m and reaches up to 3,850m.
Astonishingly, he describes it as being "easy to finish".
"That's not to say it's not difficult," he concedes.
" More than 60 hours have passed since Hawker left Everest Base Camp for the 320km run down to the Nepalese capital, a journey with over 10,000m of ascent and 14,000m descent. There are no other competitors, no one to beat but herself, no prize money or podium moment – only the breaking of her own records on a trail which has come to hold a special significance for the British ultra-runner.
She manages to pull herself to her feet and begins to put one in front of the other, moving through the heavy rain to the stadium finish line where a few friends are waiting with beers and hot, sweet tea. She remembers feeling relief at the end of the race but also a "loss of purpose".
"Ironmans (long-distance triathlons) and races like the Marathon des Sables (Md S) are the new marathons," explains Tobias Mews, an ex-army adventure athlete who chronicles his favourite runs in 50 Races to Run Before You Die (£16.99, Aurum Press, out 2 March). But as soon as you creep over that into the ultra category it's all in your head." The Md S is a 156-mile, six-day race across the Moroccan Sahara.
Before running took over she worked as an environmental scientist for the British Antarctic Survey.
She has been slowed by injury over the past few years, but is tentatively coming back into form and completed an 80km race in Nepal on 2 January.
She has also been using her time to plan her own ideal race for 2016, the Ultra Tour Monte Rosa (UTMR), a 116km trail across the Italian and Swiss Alps, her favourite training ground when she was preparing for the Mont Blanc races.
"It's a life-changing event, and it's very difficult to do well in, but you're looked after." "I'm at that stage where I'm looking for something more interesting than your standard race.
I want a degree of self-sufficiency, navigation and the jeopardy factor." An "ultra" race can mean anything over 26.2 miles, and is often 50 miles, 100 or even more.