Prince William doesn't know if he will be able to trust his brother Prince Harry and sister-in-law Meghan Markle again due to their continuing pattern of sharing private details of royal life with the world.
Since quitting The Firm back in 2022, the couple have given interview after interview making countless shocking claims about family matters - and later this year Harry is publishing a tell-all memoir.
Harry started speaking about personal issues before he had even packed his bags for the US, opening up about his relationship with his brother during a documentary for his tour of South Africa as working royals.
In his new book William at 40: The Making of a Modern Monarch, which is serialised in the Daily Mail, royal expert Robert Jobson claims the Duke was "simmering with resentment" when he watched the programme.
A member of his inner circle tells Robert: "To say William felt deeply let down would be an understatement. He wasn’t sure if he could ever fully trust his brother again,’ said one member of his circle."
And just last week, Harry sat down yet again to talk about his family while promoting the Invictus Games. He shared details of his private meeting with the Queen during his secret visit to the UK and refused to answer questions about missing William.
However Robert believes that William has been most upset by Harry and Meghan's attempt to use Sussex Royal in their post-royal lives, despite being banned from using the word royal in any of their branding.
Of their decision to try and use it anyway, a source tells Robert: "That was it for William – he felt they’d blindsided the Queen in such an insulting and disrespectful way."
The book also talks about William's relationship with his father Prince Charles and step-mother Camilla.
Robert claims that Charles hates confrontation while William has a fiercer temper.
As well as having "blistering rows" with the Duchess of Cambridge, in which they both "give as good as they get", Robert says Wills rows with his dad.
He believes this means Charles "treads carefully" with his eldest son and choses not to address his lack of respect.
Charles respects the hierarchy of the family and also lets his mother lead the way, the book suggests William doesn't do this with his father and instead sees them as equal heirs.
But while Charles won't address this, Robert suggests it's a very different case with Camilla who isn't afraid to point out the royal protocol and will "put him in his place".
An insider tells the book: "The truth is the Duchess feels it is her duty to protect the Prince of Wales from himself sometimes. He is going to be King, and she doesn’t mind reminding others in the family of that now and again – and that includes his son and heir.
In the book Robert also looks ahead to William's role as King - but believes he'll be a very different Monarch to the Queen and Charles.
He claims William has been "thinking deeply" about what he wants his time on the throne to look like, and doesn't believe he'll be as passive as his grandmother.
Robert also believes William will be more private than his predecessors and will be "more robust" at challenging advice from those around him.
Earlier this month, research found half of Britons think Charles should step aside and let William become King next.
The Ipsos research found that 42% of people think Charles should step aside for his son William to take the throne. This compares with 24% who think the prince should not stand aside for the duke, while 29% do not have strong feelings on the issue.
However, the survey also suggests that 48% of people in the UK still believe Charles will do a good job, compared with 19% who think he will do a bad job and 27% who think he will do neither a good nor bad job.
The research, which consisted of interviewing a representative sample of 2,055 British adults on March 24 and 25, also found that the proportion of people who view Charles favourably has increased since 2018 to 43% – up 11 percentage points.
William at 40: Making of a Modern Monarch is out on May 5.
