For years, Prince Harry and Kate Middleton were so close that they could easily have been mistaken for brother and sister.
He jokingly called her 'Cath' and declared she was 'the sister he never had', while the pair were often seen giggling and sharing cheeky jokes at public events.
Pals praised the royal duo's 'strong bond', adding that Kate helped bring out Harry's 'fun side'.
It was even the Duchess of Cambridge who helped engineer a conversation between warring Prince William and Harry at Prince Philip's funeral, seemingly not taking sides.
But royal commentator Duncan Larcombe told OK! Magazine that the once unshakable bond has been broken.
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"Kate was, as Harry said, the sister he never had and clearly that is not the case any more," he said. "Those days are long in the past."
The first signs of trouble surfaced in the run up to Harry and Meghan's 2018 wedding amid reports of a tearful row at a bridesmaid dress fitting.
Kate Middleton and Prince Harry were often seen whispering and giggling (Getty)
Harry called Kate the 'sister he never had' (The Daily Mirror)Sources initially claimed Meghan had made Kate cry. Three years later, Meghan refuted those allegations, insisting to Oprah Winfrey that it had been 'the other way round'.
"She (Kate) was upset about something, but she owned it, and she apologised. And she brought me flowers," said Meghan.
"There wasn't a confrontation and I don't think it's fair to her to get into the details of that because she apologised, and I have forgiven her.
"What was hard to get over was being blamed for something that not only I didn't do, but that happened to me."
But the Duke's new memoir reportedly claims Meghan Markle was left in tears as The Princess of Wales wanted Princess Charlotte's bridesmaid's dress remade.
Harry, Kate and William share a laugh with Prince Philip in happier times (Getty Images)And it appears that for the first time, Harry has opened up about what happened in his new memoir, Spare. The book isn't out until next week, however an extract seen by Page Six details Harry's account of the now infamous row.
According to the US site, Kate messaged Meghan to tell her Charlotte's dress was "too big, long and baggy" and that the youngster "burst into tears when she tried it on".
The book reportedly claims that Kate was told to bring Charlotte and the dress to a tailor but the then Duchess of Cambridge said that the dress needed to be remade, with her wedding dress designer agreeing with this.
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However, it is reportedly later claimed that Kate did take Charlotte to the tailor, with Harry writing he later found wife-to-be Meghan in tears following this. However, he is said to add that Kate later apologised and gave Meghan flowers and a card.
Harry caused outrage when he was pictured wearing the Nazi uniform in 2005 (AFP)Then there was an alleged disagreement between the pair over Meghan's alleged treatment of Kate's staff at Kensington Palace. Meghan has denied all accusations of bullying staff.
And in a leaked extract from his new memoir Spare, Harry shifted some of the blame for his Nazi outfit scandal to his brother and sister-in-law.
He writes about asking for William and Kate 's advice on choosing between two outfits - a pilot's costume or the Nazi uniform.
In a segment of the book, obtained by Page Six, Harry writes: "I phoned Willy and Kate, asked what they thought. Nazi uniform, they said."
He goes on to say that when he went home and tried it on for them, they "both howled".
Prince Harry with William and Kate during the 20th Commonwealth Games in July 2014 (Getty Images)"Worse than Willy's leotard outfit!", he adds. "Way more ridiculous! Which, again, was the point."
Meanwhile, in Meghan and Harry's Netflix documentary, they again took aim at Kate, accusing her of being overly-formal on their first meeting.
Meghan said: "Even when Will and Kate came over, and I met her for the first time, they came over for dinner, I remember I was in ripped jeans and I was barefoot.
"Like I was a hugger, I've always been a hugger. I didn't realise that that is really jarring for a lot of Brits. I guess I started to understand really quickly that the formality on the outside carried through on the inside."
William, Kate, Meghan and Harry separated their offices after a series of rows (PA Archive/PA Images)For Kate, sources say those comments were a painful reminder of the space that's grown between her and Harry.
"Kate feels hurt and betrayed that Harry would do this to her, too, especially as the pair used to be so close," a source told Us Weekly.
The bombshell memoir is set to be released on Tuesday - just hours after the airing of two interviews Harry has given to ITV in the UK and US TV show 60 Minutes.
It's set to be a tense time, not least for King Charles, Prince William and his wife Kate, who will celebrate her 41st birthday the day before.
This story is based off a translated version of Prince Harry ’s memoir Spare. Spare published by Penguin Random House will be available to buy in the UK on January 10.