Watch: Prince William and Prince Harry to walk behind Prince Philip's coffin at funeral
Prince Philip thought Prince Harry and Meghan Markle's interview with Oprah Winfrey was "madness" and said "no good would come from it".
Gyles Brandreth, Philip's biographer, said the late royal did not agree with the Duke and Duchess of Sussex's decision to step back from their senior royal duties, but eventually was resigned to it, saying "it's his life".
Philip, who died on 9 April at the age of 99, was in hospital when Harry and Meghan's interview with Winfrey aired in the US and the UK. He spent four weeks in two different hospitals being treated first for an infection and then for a pre-existing heart condition.
It was reported that the Duke of Edinburgh, who gave up a burgeoning naval career to support the Queen when she acceded at the age of 27, was being shielded from the worst of the fallout after the explosive two-hour interview.
Brandreth, writing in the Daily Mail, said: "I know from someone close to him that he thought Meghan and Harry's interview with Oprah Winfrey was 'madness' and 'no good would come of it'."
However, Philip was not concerned that he was in hospital while the interview aired, and was not against TV interviews, but his reaction stemmed from his advice over the years was always "don't talk about yourself".
Of Harry and Meghan's decision to step back, Brandreth said: "The Duke of Edinburgh was not pleased, nor did he believe that Harry and Meghan were doing the right thing, either for the country or for themselves.
"Contrary to the popular caricature of him, the Duke of Edinburgh was neither judgmental nor unfeeling."
But the former MP reported that Philip had sympathy with the "couple's mistrust of the media (he had had his own run-ins with an intrusive Press over the years) and even more so with Harry's desire to 'do his own thing in his own way'".
He even told Brandreth: "People have got to lead their lives as they think best."
The revelations come as Harry landed back in the UK on Monday morning to attend his grandfather's funeral on Saturday.
The Duke of Sussex, 36, arrived alone, having had to leave his wife Meghan in the US. She is pregnant with their second child and was not given medical clearance to fly, their spokesman said.
All eyes will be on the Dukes of Sussex and Cambridge as the brothers reunite in person for the first time since the March 2020 Commonwealth Day service.
John Major, the former prime minister who was the princes' guardian in 1997 after their mother Princess Diana died, said they should try to mend the rift quickly.
He told The Andrew Marr Show: "The friction that we are told has arisen is a friction better ended as speedily as possible.
"And a shared emotion, a shared grief because of the death of their grandfather, I think is an ideal opportunity.
"I hope very much it is possible to mend any rift that may exist."
Watch: Harry 'back in the UK' ahead of Duke of Edinburgh's funeral on Saturday
While the US is not on the red list, Harry still has to quarantine on arrival because there are no travel corridors in place in the UK.
However there are exceptions in the rule to allow for people to attend funerals on compassionate grounds, so he will be allowed out for Saturday's ceremony.
Guidance published on the government’s website states: “You can leave your place of self-isolation in limited circumstances, including on compassionate grounds.
“This includes attending a funeral of a household member, a close family member or a friend (if neither household member or close family member can attend the funeral).”
It adds: “You must continue to self-isolate at all other times.”
That would make it difficult for the two princes to arrange any face-to-face meetings.
Harry would have had to return a negative COVID test three days before he travelled and completed a passenger location form to show where he would be staying when he landed in the UK.
He will have to take tests on day one and day eight of his quarantine.
The prince could opt to take part in the test-to-release scheme, getting a private test five days into his quarantine which would then allow him out early if it's negative. These cost £130.
He risks a £10,000 fine if he breaches quarantine or £2,000 if he misses one of the tests.
He would have to socially distance from all other mourners at the funeral, because he is not in their household.
Harry will be one of only 30 mourners at the funeral under the current coronavirus regulations, after Boris Johnson decided not to attend to allow more family members to go.
It would have been a large ceremonial royal funeral but the restrictions mean it will be smaller in size and out of the public eye to avoid crowds gathering to see his coffin.
Watch: PM chooses not to attend Philip’s funeral because of coronavirus guest limits