Amid their estrangement, King Charles has one major regret over how he raised son Prince Harry, according to a royal expert.

“Prince Harry and King Charles were very, very close. They got on incredibly well,” Ingrid Seward, the author of My Mother and I, told Fox News Digital on Monday, April 1. “I think Charles probably regrets that he wasn’t strict with Harry and [Prince] William.”

Seward continued, “Diana allowed them to do, more or less, what they wanted, which was very fashionable in those days,” adding that Charles, 75, went along with Diana’s “freestyle of bringing up children.”

“You let children just get on with things. I think Charles probably regrets that he wasn’t a bit stricter, because it might’ve given both boys a few more boundaries,” the author said. “Children all need boundaries, and I don’t think they had too many.”

Charles and Harry, 39, have had a strained relationship since he and wife Meghan Markle stepped down as senior members of the royal family in 2020. 

“I will always love him, but there’s a lot of hurt that’s happened,” Harry said of his father during a March 2021 interview with CBS. “I will continue to make it one of my priorities to try and heal that relationship.”

He went on to explain how his family “literally cut [him] off financially.”

“I [needed to be able to] afford security for us,” the Duke of Sussex continued. “[I was cut off] in the first quarter of 2020. But I’ve got what my mom [Princess Diana] left me and without that, we would not have been able to do this.”

Harry and Meghan, 42, ultimately relocated their family to California, where they live with their son Archie and daughter Lilibet. 

The father-son duo have reunited just a handful of times since the Sussexes departure, including at the funeral services of Charles’ father, Prince Philip, in April 2021, and his mother, Queen Elizabeth II, in September 2022. 

Most recently, Harry flew from California to London to be by his father’s side for a brief visit just one day after the palace announced the king’s cancer diagnosis in February. 

“Harry flew to London but only spent 45 minutes with his dad at Clarence House before rushing off to Las Vegas to present at the NFL Honors,” an insider exclusively told In Touch, noting that the Duke of Sussex could have “easily canceled” his awards show appearance. “The visit came off as more of a PR stunt than a son who was seriously concerned. Now, whatever truce Harry and Charles may have had, it’s over.”