Sir Ranulph Fiennes has abandoned his attempt to reach the summit of Mount Everest, his team has said.
Sir Ranulph, 61, was raising money for the British Heart Foundation
The 61-year-old was making his final move towards the 8,850 metre (29,035ft) peak when he was forced to pull out.
A team spokesman said the explorer decided he was "pushing himself too hard", adding that poor conditions were also to blame.
He had been trying to become the first Briton to reach both poles and conquer the world's highest mountain.
The Jagged Globe team had announced on Friday that Sir Ranulph had reached the last stop on his route to the summit, located at a height of 8,400m (27,560ft).
It said the final push to the peak had been expected to last 10 hours, but one hour after leaving the camp on Saturday the adventurer decided to turn back.
"He was really concerned for his health. He decided he was just pushing himself too hard," team spokesman Tom Briggs said.
"At 61, he is very old to be doing something of this magnitude, despite the fact he has got the most amazing track record. He will obviously be disappointed.
"It has been an appalling weather year on Everest. On a better weather year, Ran's chances would have been better."
Sir Ranulph - who owns a farm on Exmoor in west Somerset - had a heart attack in 2003 followed by bypass surgery, but months later broke records by completing seven marathons on seven continents in seven days.
A few months later, in February 2004, he was widowed when his wife of thirty-four years, Virginia, known as Ginny, died after a short illness.
The explorer is famous for a three-year transglobe expedition - the first successful circumnavigation of the world on its polar axis - which was completed in 1982.
He is also well-known for his attempts, along with Dr Mike Stroud, to reach the North Pole unaided and a 97-day trek across Antarctica.
Sir Ranulph will return to the UK at the end of next week, after a medical check-up.
He was attempting to raise £2m for the British Heart Foundation. Seven of the 11 climbers in the team reached the summit.