The royal called the divorce claims "malicious" and admitted that her "state of health is still fragile."
Tom Bower said Thomas Markle Sr. had wanted cameras to film his visit to Windsor Castle to see the duchess and her children.
Thomas Markle Sr. reportedly suffered a stroke Monday evening and is now recovering in the hospital.
Tom Bower is releasing an unauthorised book about the Duchess of Sussex sometime this year.
Thomas Markle Sr. is forced to cancel his trip to the U.K. for the Jubilee after he suffered a major stroke on Monday.
The Duke and Duchess of Sussex shared a kiss on stage after his team won the tournament.
Her Majesty started the walkabout in the 1970s as a way for her to meet and interact with the public during royal visits.