James Hewitt, who famously had an affair with Princess Diana, was “fighting for life” after suffering a heart attack and a stroke.
The former army officer was taken to an intensive care unit after having an emergency operation for a pre-existing illness.
He was given “just a slim chance” of survival.
James was treated at the Derriford Hospital in Plymouth before being transferred to the Royal Devon and Exeter Hospital for specialist treatment.
“He had a pre-existing illness, then got seriously ill,” a source told the Sunday Mirror. “Suddenly it got very critical and he was rushed to hospital.
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“It was pretty serious but hopefully we’re all okay now. He is recovering.”
In March, James was interviewed on an Australian TV show and was asked whether he is the father of Prince Harry – a long-held rumour.
“No, I’m not,” he said.
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When pressed on the constant speculation about Harry’s paternity, he said. “It’s worse for him, probably, poor chap.”
He and Diana met at a party in Mayfair, London, in 1986, when she was 25 and he was 28. They reportedly began their five-year affair after she hired him to teach her to ride horses.
Prince Charles was reportedly having an affair with Camilla Parker Bowles at the time.
Ken Wharfe, Diana’s former protection officer, told how he guessed Diana was having an affair.
“Hewitt, a natural womaniser, gave her the attention and affection she relished, and then the passion she yearned for,” he wrote in his book.
“At first, Diana refused to concede to me that her affair was anything less than innocent.
“I would assure her that I had no interest in anything but her safety, but she must have thought I was stupid or deaf.”