Explorer Henry Worsley has died after suffering exhaustion and dehydration during an attempt to cross Antarctica.
The ex-Army officer, 55, had been rescued 30 miles short of his goal of crossing the continent unaided.
In a statement, his wife Joanna said she felt “heartbroken sadness”. Mr Worsley, from Fulham in London, died of “complete organ failure”, she added.
Mr Worsley was trying to complete the unfinished journey of his hero, Sir Ernest Shackleton, 100 years later.
“My summit was just out of reach”, he said in his last audio message from Antarctica on Friday.
“When my hero, Ernest Shackleton, was 97 miles from the South Pole on the morning of January the 9th 1909, he said he’d shot his bolt,” he said.
“Well today I have to inform you with some sadness that I too have shot my bolt.”
Prince William has led the tributes to Mr Worsley, who was raising money for the Endeavour Fund, a charity which helps wounded servicemen and women and is managed by the Royal Foundation of the Duke and Duchess of Cambridge and Prince Harry.
The duke, who was patron of the expedition, said he and Prince Harry had lost a friend, as he paid tribute to Mr Worsley’s “selfless commitment” to fellow soldiers.
“He was a man who showed great courage and determination and we are incredibly proud to be associated with him,” he said.
The princes pledged to ensure Mr Worsley’s family, which includes his two children, Max, 21, and Alicia, 19, received the support needed “at this terribly difficult time”.
The ReMark Group, which was supporting Mr Worsley’s effort, said in a statement: “When Henry was picked up by Antarctic Logistics and Expeditions (ALE), he was suffering from exhaustion and dehydration.
“He was flown to a hospital in Punta Arenas [in Chile] where he was found to have bacterial peritonitis.
“This resulted in Henry undergoing surgery but in spite of all the efforts of ALE and medical staff, he succumbed.”
Peritonitis is inflammation of the peritoneum, the thin layer of tissue that lines the inside of the abdomen. According to the NHS, most cases come from injury or infection in another part of the body.
On Instagram, David Beckham said he was “lucky to have met Henry”, who had “served our country for so many years”.
And adventurer Bear Grylls tweeted: “We are devastated by this loss. One of the strongest men & bravest soldiers I know. Praying for his special family.”
Gen Sir Nick Carter – the head of the Army and a close friend of the explorer – said Mr Worsley had “extraordinary traits of courage and determination” but he did it all with the “most extraordinary modesty and humility”.
Mr Worsley began the 1,100-mile (1,770km) coast-to-coast trek in November, pulling a sledge containing his food, tent and equipment.
The plan was to cross the continent “unassisted and unsupported” – with no supply drops or help from dogs or any other source.
Henry Worsley retired from the British army in October 2015 after a 36-year career, serving with the Royal Green Jackets and later the Rifles Regiment.
Since childhood he had a passionate interest in the lives of the Antarctic explorers of the Edwardian era – Sir Ernest Shackleton, Captain Robert Scott and Roald Amundsen.
In 2008, Mr Worsley led an expedition to commemorate the centenary of Shackleton’s “Nimrod” journey, which pioneered a route through the Transantarctic Mountains to a point just 97 miles (156km) short of the South Pole.
To commemorate the centenary of Scott’s and Amundsen’s expeditions, Mr Worsley returned to Antarctica in 2011, leading a team of six soldiers re-tracing the original 1912 to the South Pole.
He led the Amundsen route – a 900-mile (1448km) unsupported journey – and in doing so, he became the only person to have completed the classic Antarctic routes of Shackleton, Scott and Amundsen.
Mr Worsley’s latest expedition again followed in the footsteps of his idol Sir Ernest Shackleton, who set off to cross Antarctica in 1914. The ill-fated trip saw his ship Endurance became trapped in ice for 10 months before it sank, but not one of the expedition’s members died.
Sir Ernest Shackleton’s granddaughter Alexandra said Mr Worsley’s death would be a “huge loss to the adventuring world”.
“He was very energetic, very keen on testing himself, seeing how far he could get with his endeavours,” she said.
“The whole point of this one was that Henry was doing it on his own. I suppose you could say he was doing more and more adventurous and interesting things.”
Mr Worsley had passed his target of raising £100,000, and the Endeavour Fund said in a statement that it was “devastated” by his death.
In October, he told the BBC he expected to lose two stone (12.7kg) during the challenge.
He said his journey should take 75 days and he would take enough food for 80 days, adding: “I could make it last a bit longer.”
Asked if he was “mad” to take on the challenge, he said: “There is no black art to sliding one ski in front of the other.
“What will drive me on is raising money for these wounded soldiers.”