Meghan Markle and Prince Harry were told to they could not switch seats at the Platinum Jubilee celebrations by orders of the Queen, according to royal author Tom Bower.
Mr Bower, writer of Revenge, has catalogued the series of events which led to the falling out between the Duke and Duchess of Sussex and the rest of the royal family.
Among Mr Bower's claims have been that Meghan made Kate Middleton cry on her wedding day, had her Suits scripts monitored, and left the UK because she couldn't understand why she wasn't more important.
Meghan Markle
PA Features Archive/Press Association Images
But speaking on Pod Save the Queen, Mr Bower revealed another story he had been told which didn't make its way into Revenge.
He said: "I was told, unfortunately too late for the book, they were meant to turn up at Wellington Barracks to get on the coach which was set up for the minor royals to go to St Paul's for the Jubilee service.
Meghan Markle
PA Features Archive/Press Association Images
"They arrived deliberately late so the bus had gone and they could make a grand entrance from a car so they could be seen on the steps, which Netflix obviously needed.
"And then as they walked down the aisle, they get to the seats in the row they are assigned and I'm told they then asked six other people sitting this side of the aisle could they move down so they could sit on the aisle itself.
"And the usher apparently said to them 'you can't, you're sitting in seats eight or nine' or whatever it was and Harry said 'why?'
"And the usher said 'that's what your grandmother ordered'. I'm told that from a military man."
Heat magazine has reported that Meghan is furious at the book's release and some of the allegations it contains.
Sources close to the Sussexes are reportedly prepared for more stories to come out, fearing that Revenge "is just the tip of the iceberg".