Prince Harry and Meghan Markle have been criticised for trying to make King Charles' Coronation "all about them".
The Duke and Duchess of Sussex have been branded branded "rude" for failing to respond to their invitation to the historic event on May 6.
The couple are yet to confirm if they will be attending the Coronation, despite it being less than a month away. The cut-off point for RSVPs has also reportedly passed.
Speaking about their delay in responding, royal biographer Robert Jobson said: "They have been given an RSVP, they have missed that deadline. It's getting a little rude now to say the least.
"You are either going to support your dad on his moment of destiny or you are not.
"But don't just keep everyone guessing because that then creates the whole tabloid speculation, when it's basically saying it's all about them, and frankly it's not all about them, it really isn't."
During an appearance on TalkTV, Robert told host Jeremy Kyle that the Coronation would be "an ideal opportunity" for King Charles to see his grandchildren.
He added that ultimately, the King will forgive Harry if he decides to snub the Coronation.
"I think the King, being a dad, will be forgiving of so much with his son, your children, you always are. It’s a difficult position for him," Robert said.
A leading publicity expert has suggested the Sussexes are using their Coronation decision to their advantage to create "the most drama and the most speculation".
Speaking to The Mirror, Matt Yanofsky said: "It's to their advantage to drag out whether or not they will attend.
"If they instantly declined, the story would have died after a few days. If they RSVP'd, they'd get a tad more press in the lead-up, but it would lack the drama of a will-they-or-won't-they scenario."
The PR expert and The Moment Lab founder added: "Holding off on making a choice creates the most drama and the most speculation.
"If you're someone whose main PR move is to create drama, this is the correct move.
"This is what a soap opera character would do, and they are essentially real-life Royal soap opera stars."
Matt also said it would be advantageous for the Duke and Duchess of Sussex to attend the Coronation to create more publicity for themselves.
"If I was advising them, I would advise them to attend. They've sold most of the drama they have to sell about the royals.
"They need a new storyline and attending would be a story," he said.
Watch Jeremy Kyle Live on TalkTV Monday to Thursday at 7pm. Available on Sky 522, Sky Glass 508, Virgin Media 606, Freeview 237 and Freesat 217 as well as on DAB, Amazon Fire TV, Apple TV, Samsung TV Plus, YouTube, the Talk.TV website and TalkTV iOS and Android apps.
