Everest explorer Richard Parks a 'ticking time bomb'
Welsh adventurer Richard Parks said he was forced to abandon his expedition of Mount Everest after a blood test revealed he was a "ticking time bomb".
The 38-year-old had been attempting to become the first person to take blood and muscle samples at the summit to investigate the effects of altitude.
But after reaching Camp Two on the mountain, he discovered he had dangerously thick blood that left him at risk of a heart attack or stroke.
"I could have died," he said.
The former Wales rugby international, originally from Pontypridd, was climbing without using supplemental oxygen as part of the collaborative British research expedition called Project Everest Cynllun.
It was hoped data from the world-first bid would allow researchers to explore the mechanisms underpinning dementia and resilience.
Parks had climbed to 6,400m (21,000ft) above sea level earlier this month - the summit is 8,848m (29,029ft) - when his team decided to check his blood.
"If it wasn't for that unscheduled blood test I could have obliviously been stood on the summit now or I could be dead," he told BBC Radio Wales' Jason Mohammad programme.
"At sea level this would have been a very dangerous situation. But at the altitude I was and with the exertion levels I was under I could have been a ticking time bomb."
He added he was undergoing more tests to find out what caused the anomaly in his blood.
Despite feeling disappointment about the outcome of the trek - which he had been working on for two years - he said he was pleased scientists could still use the data he had collected for their work.
He added: "I think in this chapter of my life, success is not black and white as it was on the rugby field.
"I'm an ambitious man and I was really passionate about this project. It's been a difficult situation to process."
Parks, who had previously climbed Everest and trekked solo to the South Pole, said his next challenge was starting a degree in psychology at the University of South Wales in September.
"I'm going to take some time to reflect and spend time with loved ones," he added.