King Charles forced Prince William and Prince Harry to wear suits to breakfast when they were kids, according to a royal expert

• Royal expert Katie Nicholl said Harry and William wore suits to breakfast when they were kids.

• She said Charles banned jeans and sneakers when they came to stay with him after his split from Diana.

• Diana, meanwhile, took them to McDonald's, the movies, and theme parks.

After their parents' very public separation, Prince William and Prince Harry began splitting their time between the royal estates that King Charles and Princess Diana called home.

And, according to royal reporter Katie Nicholl, Charles and Diana had very different parenting styles.

In her book "The New Royals: Queen Elizabeth's Legacy and the Future of the Crown," which was released in October, Nicholl details what life was like for the two young princes following Charles and Diana's split.

"By the mid-nineties, Charles and Camilla were conducting their love affair behind closed doors, careful not to be photographed together," Nicholl wrote. "The prince divided his time between St. James's Palace and Highgrove, where he could be close to his mistress. Diana was based at Kensington Palace, while William and Harry bounced between all three households and school."

When they stayed with their father, Harry and William "enjoyed country pursuits such as shooting and stalking" and their nanny allowed them to enjoy the "fresh air, an air rifle, and a horse," Nicholl wrote.

But it remained a formal affair. Ken Wharfe, Diana's former protection officer, told Nicholl that he always saw the boys in Turnbull & Asser suits.

"Charles wouldn't allow them to wear jeans and trainers at breakfast," Wharfe said. "He had an almost Victorian attitude to things like that."

Life was very different at Kensington Palace, where Nicholl said the boys enjoyed fast food and fewer rules.