Gazing out from the 8611m summit of K2, world record-making adventurer Adrian Hayes "glimpsed the curve of my own soul".
"It's a profound experience," the mountaineer, polar explorer and ex-SAS soldier tells the Weekend Herald.
Standing atop the "Savage Mountain", at a height where human life cannot be sustained, "and looking with a mixture of awe and bewilderment at the world below".
But the night before making his perilous ascent, Hayes penned a letter to his teenage son and daughter and another to his unborn child.
"These were the letters which I hoped they would never read," he says in his new book One Man's Climb: A Journey of Trauma, Tragedy and Triumph on K2.
"For if they did, it would mean that I wasn't coming back."
Hayes, in New Zealand on Monday to begin an international tour to promote the book, knows all too well the ultimate price so many have paid trying to conquer the planet's second-highest mountain.
A year earlier on K2, he farewelled celebrated Kiwi climber Marty Schmidt and his son Denali as they strode off in bright sunshine for a possible final push to become the first father and son to reach its peak.
"Best of luck guys," Hayes recalls telling the pair. "Look forward to hearing how it was tonight.
"And off they went."
An avalanche would claim both Schmidts' lives, entombing them under the snow in one of the remotest parts of the planet.
Anguished by their deaths, the loss of "a father and son... tragic beyond any comprehension", Hayes had to break the terrible news to the world.
It was an "overwhelming, exhausting" experience, leaving him ill and in "intense sadness" upon his return to his home town of Lymington in Hampshire, England.
His daring journey back to K2 – which he will bring to light for audiences at events in Auckland, Wellington and Christchurch this coming week – was inspired by Sequoia Schmidt.
A US-based book publisher, the daughter of Marty and sister of Denali supported his decision to make his second attempt on the mountain and encouraged him to write his book.
It comprises more than just the profound events of K2, he stresses.
"It developed into as much a lesson in human development, society, real teamwork and our lives in the world below as it is the story of climbing K2," says Hayes, a professional leadership, team and personal coach, who delivers programmes across the world.
"I like to think of it as a compass for conquering the mountains in all of us, enveloped in a true story from the very edge of existence on Earth."
When Hayes touches down in Auckland tomorrow it will be his first time back in three decades, since working for six months sheep farming in Methven and Gore as a 20-year-old.
"I had a lovely time," he recalls.
"Most weekends, I hiked with a mate up in the mountains. You're on your own and that was what was fantastic about it."
His South Island farming stint was in the middle of a planned year-long OE at 16, which turned into nearly seven years of international adventuring, scaling mountains, sailing and skydiving.
"As a 12-year-old I had pictures of polar explorers and mountaineers on my wall, was obsessed with travelling the world, wrote down my goals, including living on a desert island, summiting Everest, walking to the North Pole," Hayes says in One Man's Climb.
"I made this [resolution], I'm going to experience everything I can in this life," he says.
Back in the UK as a long-haired singer and guitarist in a rock band, Hayes decided to take a different tack and try out for the armed forces.
Superbly fit, determined and adventurous, he became an SAS reservist at 22.
His intense training over the next two years set a physical and emotional base for his subsequent world-beating expeditions.
"I discovered that I had this ability to keep on going," he says, recalling one 60km-plus march up and down a mountain range in "appalling weather".
"I just [seemed] to get in the zone."
After two years of Special Forces service, he applied for officer training and graduated from Royal Military Academy Sandhurst and served as an officer in the Gurkhas for eight years, making acting major.
He played fullback for a British Forces rugby team, his "great claim" being able to slot sideline penalties and conversions with either foot.
Leaving the army, Hayes went into business, including seven years as the Middle East sales director for Airbus, but continued his adventuring life with longer and riskier expeditions.
His achievements have included:
• Summiting Mt Everest, the world's highest mountain. An "absolutely surreal, quite incredible experience", but a fearful one too after his oxygen mask failed. "That seven hours to get off the top, get down, was just the most sobering experience I've ever had. All I wanted to do was fall asleep... I [had to] keep pushing, pushing, pushing."
• Trekking to the North Pole. "It was an ordeal against pain pretty much the whole two months... We fell in, we got frozen. Pulling the sled [for] 15 hours, 16 hours a day. It was absolutely brutal."
• Reaching the South Pole. "[It] has an amazing beauty... The most amazing place I've ever been in this world."
• Scaling Everest and reaching both poles made him the 15th person to conquer the three extremes of Earth's latitude and altitude. He made it into the Guinness World Records for completing the Three Poles Challenge in the shortest time.
• The longest unsupported snow-kiting expedition in the Arctic – a 3120km vertical crossing of the Greenland ice cap. Recognised by Guinness World Records. A documentary film of the expedition was shown on National Geographic Channel.
• Traversing the Arabian Desert by camel and on foot for 44 days across 1600km. Two hours after the expedition set off, one of the camels "threw me off and knocked me out for about 10, 11 seconds [on] a trip that we'd been planning three years".
A next major challenge was to summit K2, on the China-Pakistan border. Climbers face a hazardous combination of high altitude, sustained steepness, technical requirements, notorious weather, snow conditions, avalanche dangers, rockfall hazards and remoteness, Hayes says.
More than 80 people have died trying to reach the summit.
Conquering K2 has "long represented the holy grail of mountaineering", Hayes says.
His first bid was in 2013 when he met Marty and Denali Schmidt. The Kiwi contingent, along with their Australian teammate, Chris Warner, were among seven teams gathered at K2 Base Camp for their attempt.
They quickly formed a bond, he says.
Marty, 53 – "friendly, very open, very chatty, very confident" – was a highly experienced mountaineer.
He had climbed and guided on many of the "eight-thousanders" – the 14 highest mountains in the world – including scaling Everest twice.
A former member of the US Air Force's elite Pararescue unit, he received its prestigious Air Medal in 1984 for rescuing people in a hotel fire.
Denali, 25, named after North America's highest mountain, was a "really nice, humble guy".
A talented artist, he had just graduated from the California College of the Arts in San Francisco.
"[Denali was] widely talented and a phenomenal skier, he was also an extremely strong climber, who had climbed and guided regularly with his father since his teenage years," Hayes says in his book.
"They were both exceedingly fit."
The trio was "always visiting each other's camps" chatting about "everything, from life, [to] New Zealand, from world politics to mountains".
Their final conversation was at Lower Camp 2, around 6600m, on the morning of July 26.
Hayes was making his way down to Base Camp in defeat after five of the other teams abandoned a thrust for the top following days of snow.
The Kiwi father and son hadn't given up, however.
"We're gonna go up to Camp 3 (7200m) today and check it out; if it's good, we'll push on tomorrow; if it's bad, we'll come back down, simple as that," Hayes recalls Marty saying.
Warner tried to make contact with the Kiwis for nearly an hour after a rostered 6pm call, before speaking to Marty, who said he and Denali had safely made it to Camp 3 and would decide how to proceed in the morning.
None of the next day's scheduled calls to the Schmidts were answered.
As the hours went by, fears grew.
The worst was confirmed when two Sherpas, moving with "astonishing" speed, made their way up the mountain the following morning to find the New Zealanders.
They discovered two scattered ice axes outside, but no sign of the father and son.
A big avalanche had hit the camp.
"100 per cent mareko cha," one of the Sherpas said over the radio.
"I knew immediately what he meant," Hayes says.
"100 per cent die," a Sherpa at base camp confirmed, "a torn look on his face."
A shocked and distressed Hayes ventured outside that night to gaze up at Camp 3 in the moonlight – "my thoughts on a father and son, buried together in a tent under a few feet of snow".
"Rest in peace, my K2 brothers," he said quietly before retreating to his frozen tent.
Warner informed family of the tragedy.
Hayes, the sole regular blogger following the expedition's abandonment, then relayed the news to the outside world via his website and Facebook pages.
Battling an intestinal condition and reflecting on the loss of the Schmidts on his return home, he found his readjustment to "so-called normal life" harder than ever.
The "contemplation, focus, communications, strategising, deep thinking" employed in his expeditions in the natural world "blown away" by a bombardment of technology, social media and materialism.
"When one tackles death head-on, when life is stripped to those bare elements and when one is in complete connection with rock, ice, sun, sky and stars, our priorities in life take on a whole new meaning," Hayes says in One Man's Climb.
"I look at… consumerism, vast possessions and flash cars with amusement – even though I'm a petrol head F1 fan.
"They mean nothing at 8000m and, in reality, should mean little at sea level.
"None of them ever bring happiness or fulfilment and, indeed, merely add to the clutter and chaos of our lives."
His sense of purpose was restored with the decision to return to K2 and challenge it once again.
Hayes designed a "brutal" training regimen to restore him to his fitness levels as an elite trooper.
Three days a week he hiked in desert mountains for up to 11 hours a day with a backpack filled with rocks for extra weight.
A fourth day he would run up a 52-floor office tower with ankle weights and a pack.
The remaining three days he ran, worked out at the gym, and went on "fast and furious" 40km cycle rides.
He returned to K2 in July 2014, part of an eight-person wider team including Kiwi Chris Jensen Burke, who has summited more 8000m peaks than any New Zealand or Australian woman climber to date.
Climbing to Lower Camp 2 to acclimatise for their ultimate ascent, they came upon the "tattered, ragged" remains of Marty and Denali's tent.
"The events of one year ago flowed right back through our minds," Hayes says in his book.
"Here, at this very spot, we'd sat down and had the last conversation anyone would ever have with our fallen colleagues.
"It was a poignant moment of reflection, of loss, of memories and of what could have been…
"The fine line between life and death."
Waking early on the morning of the attempt at the peak, Hayes sealed his handwritten letters to Alex and Charlotte, now 20 and 18, from his past marriage, and son Nicklas, now 4, who was yet to be born.
Kissing a photograph of the teens, he placed it with the letters, vowing if he didn't make it back, "I will be with you forever in spirit".
Then he "stepped out into the unknown".
At 3.20pm on Saturday, July 26, 2014, he took his final steps to the top.
"The ground fell away in all directions to the world below," he recalls in his book.
"Above me was only sky. I stood in awe looking over the elusive curvature of the earth.
"And, perhaps, glimpsed the curve of my own soul.
"I was on the summit of the mighty K2."
Writing his book, which also includes the parallel traumatic journey in his personal life, was "a cathartic exercise", Hayes says.
He hopes readers as well as audiences at his promotional events will be moved, inspired and take away some powerful lessons for their own lives.
He says he is driven by "that mantra, life is for learning".
"And that means stepping out of comfort zones… pushing your limits… trying new things, reinventing yourself."
"It's the challenges that define who we are."
Hayes will retrace his epic K2 journey at his events, including an array of videos and photographs.
He will also speak about his sustainability and social causes.
The qualified paramedic provides annual medical camps in Nepal and is a patron of charities Population Matters and CHASE Africa.
Hayes leaves for Sydney on Saturday for the Australian leg of his book promotion tour, followed by Hong Kong, Singapore, South Africa and North America.
Before leaving K2, Hayes paid a last visit to the Schmidts' plaque at the Gilkey Memorial at the base of the mountain.
The memorial was erected after the death of Art Gilkey, who died during a 1953 expedition of K2 but it has since become a memorial for others who have died on the mountain.
"My mind flashed back to my childhood, to the 12-year-old boy who determined that only with the honest knowledge that one day I would also die, could I truly begin to live," Hayes says.
"What we did in life echoes in eternity.
"That's why my fallen friends here died; because they truly lived."
Adrian Hayes' speaking events:
One Man's Climb
By Adrian Hayes
Pen & Sword Books, distributed in NZ by South Pacific Books