The Duchess of Cornwall began to understand Princess Diana's "discontent" with royal life before she married Prince Charles, a new book claims.
According to author and former Vanity Fair editor Tina Brown, Camilla struggled with Charles' "regimented" lifestyle, much like Diana.
And in her book The Palace Papers, out later this month, she claims that the now duchess started to understand the prince's former wife's frustrations with royal life.
Writing in the book, which had an excerpt published in The Telegraph, Ms Brown writes: "The Prince’s routine was relentless. He never ate lunch, and breakfasted on the same birdseed and peeled fruit every morning.
"Punctuality had never been Camilla’s strong suit, but Charles expected her to be ready for engagements at his own regimented pace. When she asked where they were going, he would snap: “Haven’t you read the brief?” One of her friends at that time told me that she had even started to feel some empathy with Diana’s manifold discontents."
Meanwhile, the extract also claims that Camilla once believed there was no upside to being the wife of the Prince of Wales.
Ms Brown adds: "For a while, she had thought that there was an upside to not being Charles’s wife. She had always hated flying, speaking in public, dressing up and getting press attention.
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"She had never had a calendar filled with things she didn’t want to do, which essentially defines the royal way of life."
However several years later in February 2005, it was announced that Camilla would marry Charles and on Saturday, they celebrated their 17th wedding anniversary.
Upon her wedding, Camilla became a stepmother to Charles' sons Prince William and Prince Harry.
And in a separate interview with The Telegraph, Ms Brown says Harry "can't stand" his father's second wife and doesn't want her to be Queen.
She added he will "go after" the royal couple in his explosive memoir, which is being released later this year, and claimed that his relationship with William is "very bad".
Ms Brown explained: "William has accepted Camilla in terms of what she means to his father. He’s been grown-up about it. 'My father loves this woman, I can’t fight it, so I won’t.'
"Harry, on the other hand, can’t stand Camilla, he doesn’t want Camilla to be queen, he’s very angry that it’s happening. He has not made his peace with it and he probably never will."
If true, the rift already present between Harry, 37, and wife Meghan Markle, 40, and the rest of the Firm could be further deepened.