The late Princess Diana would have a lot of "sympathy" for Prince Harry but also be "concerned about the disconnect" with his brother, Prince William, according to her royal biographer.
The Duke of Sussex will officially release his highly-anticipated memoir, Spare, on 10 January – over 30 years since Andrew Morton penned the late princess' biography, Diana: Her True Story. However, after the book unexpectedly went on sale on Thursday in Spain, a number of bombshells from the publication have already been leaked.
WATCH: The sensational release of Andrew Morton's Diana book remembered
Speaking to HELLO! before extracts from the book were leaked, Andrew said: "Presumably [Princess Diana] would have a lot of sympathy for [Harry]. The major difference is that Diana was deeply unhappy in her marriage and it's quite clear that Harry and Meghan are besotted with one another and their children.
"Any mother would be concerned about the disconnect between the two brothers and she said quite clearly to me that she saw Harry as a back-up in the nicest possible way, I'm quoting her now, for William. And she saw him, I've said this phrase before, as William's wingman, and not a hit-man."
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Harry's book Spare will be released on 10 January
And how might Diana see the release of Harry's memoir from her eldest son William's point of view?
"It depends how much is said about the relationship between the two brothers," Andrew said. "There's nothing new about brothers and sisters falling out in the royal family."
HELLO! got hold of a copy of the Spanish version of Harry's memoir, and among the explosive claims in the book is a description of a physical altercation between William and Harry, with the Duke of Sussex also describing William as his "arch-nemesis".
MORE FROM SPARE: Prince Harry believed Princess Diana was in hiding after her death
Andrew, who detailed Diana's struggles within the royal fold, pointed out a key difference between his biography and Harry's book.
"The significance, the importance of the Diana book was it exploded the fairytale for a whole generation of people and ultimately, it allowed Diana to make her own choices in life – separation, ultimately divorce and by the end of her life, she was a prominent, independent humanitarian campaigner.
"For Harry, it's rather different. He was and is happily married, so it's not about his personal relationship, it's about his relationship with the rest of the family and I think that the central misunderstanding is that the royal family is about position, not about popularity, and initially Meghan and Harry were very popular, and they felt that they should have the same position, which reflected their popularity. Well that's not the way it works."
While Buckingham Palace and Kensington Palace have both declined to comment on claims made in the book, Andrew referred to history repeating itself.
"The Queen Mother as Queen and King George VI as King George VI were very concerned when the Duke of Windsor decided to write A King's Story about life inside the royal family," he said. "Well, in the exact same parallel about two brothers who have fallen out, one younger than the other, and the sky didn't fall in on the monarchy. The monarchy survived the memoirs of Edward VIII, the Duke of Windsor, even though they were terrified that the house would fall in, but it didn't."
Andrew Morton's The Queen, £9.67, Amazon
Andrew, whose latest book The Queen: Her Life is released in a paperback edition on 19 January, said the late monarch would have been "quite equitable" about her grandson Harry's memoir, adding: "For the simple reason that other members of the royal family have cooperated with – notably Diana with me, Charles with Jonathan Dimbleby, going back, the Duke of Windsor, the Duchess of Windsor, Lord Harewood, the Duke of Kent, they've all brought out memoirs with greater and lesser degrees of discretion and publicity."
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