The veteran broadcaster is no stranger to groundbreaking interviews, having previously interviewed Harry's late grandfather, Prince Philip.
Between 1971 and 2007, the 86-year-old star had a weekly audience of over eight million people tuning into his chat show Parkinson, with a wide variety of people taking to the sofa.
However, Sir Michael says that his most daunting conversation was with Prince Philip, who he believes took an instant disliking to him during their chat.
Speaking to The Telegraph, he said: "I never felt quite comfortable with Philip, I suspected he didn't like me very much, I did have to chat to him once, for a charity, and it was not a success, at all."
But while he may have had a conversation with the late Duke of Edinburgh away from screens, Michael interviewed Princess Anne, the Princess Royal in 1980 following the kidnap attempt she suffered.
"She's formidable, you don't go mucking around with her," he told the publication.
Reflecting on Harry's upcoming memoir, Spare, which is due to be published in January, he swiped: "Oh, we await that, Pulitzer Prize-winning stuff, I'm sure," before adding: "I do think he would have made for an interesting interview if he had told the truth.
"The entire family are an explained myth, aren't they, really."
But Parkinson didn't hold back when he was questioned over The Late Late Show star James Corden, claiming he's a "comic, not an interviewer", before adding that Corden doesn't possess the skill of how to ask questions.
It had been claimed that Prince Harry had changed parts of his bombshell memoir following the death of the Queen on September 8, 2022.
Now, Omid Scobie, a friend of Harry and his wife Meghan Markle has claimed that Harry chose the name himself, a nod to him and his older brother Prince William being 'The Heir and Spare'.
Omid, who wrote the unauthorised biography Finding Freedom on Meghan and Harry wrote for Yahoo: "There were also no last-minute rewrites or edits after the Queen’s death.
"Spare's manuscript was completed almost five months before the monarch's passing, a detail that will be acknowledged in a note at the start of the book."
He goes on to claim that Harry is "owning" the "derogatory moniker" which he has had a "lifetime of being called it".