Discussing this decision, Eden told the Palace Confidential talk show: "I have heard it said that part of the reason is that the King wants to stop Archie from inheriting that title of the Duke of Sussex.
"So this might be part of that, so he has now set that precedent.
"The problem is, that he’d have to do it with all the royal dukes so he really wouldn’t want to do that to the very well-respected Dukes of Gloucester and Kent."
Earlier this month, Meghan Markle and Prince Harry released a statement addressing their children's new titles.
The Sussexes said: "The children's titles have been a birthright since their grandfather became Monarch.
Archie and Lilibet's titles as princess and prince will be used in formal settings but not every day by their parents.
"This matter has been settled for some time in alignment with Buckingham Palace."
Archie and Lilibet's titles as princess and prince will be used in formal settings but not every day.
Prince Harry is fifth in line to the throne, whilst his children Archie Harrison and Lilibet Diana are sixth and seventh in the Royal Family's line of succession.