Henry Worsley was just 30 miles from becoming the first adventurer to cross the polar region unsupported and unassisted when he fell ill on Friday.
Despite being airlifted off the ice and flown to a hospital in Chile, he was found to have bacterial peritonitis. He underwent surgery but died on Sunday aged 55.
The former Army officer’s expedition aimed to complete the unfinished journey of his lifelong hero, Sir Ernest Shackleton, in the process raising money for the Endeavour Fund, which helps wounded servicemen and women.
Prince William, who was the patron of the expedition and had waved Mr Worsley off from Kensington Palace in October ahead of the start of his trek, said he and his brother had lost a friend.
He said: “Harry and I are very sad to hear of the loss of Henry Worsley. He was a man who showed great courage and determination and we are incredibly proud to be associated with him.
“Even after retiring from the Army, Henry continued to show selfless commitment to his fellow servicemen and women, by undertaking this extraordinary Shackleton solo expedition on their behalf.
“We have lost a friend, but he will remain a source of inspiration to us all, especially those who will benefit from his support to the Endeavour Fund.”
Battling temperatures of -44C, tackling white-out blizzards and treacherous ice, the former-lieutenant colonel was 71 days into his expedition, had passed the South Pole and covered 913 miles.
After spending two days unable to move from his tent, the married father-of-two took the decision to pull out of the charity adventure after suffering from exhaustion and severe dehydration.
His wife Joanna, who flew to be by his side, said: “It is with heartbroken sadness I let you know that my husband, Henry Worsley, has died following complete organ failure.”
She paid tribute to her husband for reaching his goal of raising more than £100,000 for wounded service personnel.
Fellow adventurers Bear Grylls and Ben Fogle described their devastation at hearing the news. Grylls wrote: “One of the strongest men & bravest soldiers I know. Praying for his special family,” while Fogle wrote on Twitter: “So sad to hear that Antarctic explorer Henry Worsley @shackletonsolo has passed away. An inspiration to us all.”
Peritonitis occurs when the thin layer of tissue lining of the abdomen becomes infected. Symptoms can include swelling of the abdomen, vomiting, chills, lack of appetite and a high temperature.
In his final statement sent from Antarctica, Mr Worsley described how his desire to help wounded soldiers with their rehabilitation was the central focus of his expedition, but that he had taken the decision to call for help.
“The 71 days alone on the Antarctic with over 900 statute miles covered and a gradual grinding down of my physical endurance finally took its toll today, and it is with sadness that I report it is journey’s end – so close to my goal,” he said.