King Charles, Prince Harry reconciliation is not impossible, but will be a 'slow burn': author

King Charles reportedly wants to make amends with his estranged son Prince Harry — but peace talks won’t come easily.

The claim was made by DailyMail contributor Robert Hardman, author of "The Making of a King: King Charles III and the Modern Monarchy."

Hardman told Fox News Digital that the king, who is battling an undisclosed form of cancer, would only be willing to speak with the Duke of Sussex again once he feels his son is no longer publicly airing his grievances.

"People keep asking, 'Could Harry come back into royal life? Could he do this? Could he do that?' You never say never with the royals," Hardman explained. "But I think a good starting point is to get back to a situation where it's perfectly normal for Harry to visit the U.K. and see his father with [his] kids, and Meghan [Markle], too, if she wants to."

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Prince Harry has had a strained relationship with his family since he quit royal duties in 2020. (Isabel Infantes/Pool/AFP via Getty Images)

"It's going to be a slow burn, yes, but no, the door is not slammed shut."

— Robert Hardman, author of "The Making of a King: King Charles III and the Modern Monarchy"

"We… sense that she doesn't like coming to Britain at all," claimed Hardman about the Duchess of Sussex. "But if you get to a situation where they come over now and then to see granddad — once it happens once or twice, and it becomes normalized, they can start building from there."

"It's going to be a slow burn, yes, but no, the door is not slammed shut," he added.

Hardman believes Harry should attempt to make peace with his father if he ever desires to return to the royal fold in any capacity. He described Prince William, heir to the British throne, as "very dutiful," a royal who will prioritize the crown over his relationship with his younger sibling, which is said to be nonexistent today.

King Charles III and Queen Camilla wave as they board the Royal Australian Air Force jet via Faleolo International Airport following their visit to a farewell ceremony at Siumu Village in Apia, Samoa, on Saturday. Buckingham Palace announced in February that the monarch had been diagnosed with an undisclosed form of cancer. (Chris Jackson/Pool/Getty Images)

"William is less radical than his dad," said Hardman. "They do things differently. They have their own different opinions on certain things… But they work as a team. It all goes right back to the night that Queen Elizabeth II died [in 2022] and the royal family gathered at Balmoral Castle. Everyone is sad having dinner — except Charles, [Queen] Camilla and William. They’ve gone to Charles’ place to map out what will happen next from that moment on. They’ve said to each other, ‘We have to be a team.’"

Prince William is heir to the British throne. His relationship with his younger brother Prince Harry is said to be nonexistent. (Chris Jackson/Getty Images)

"Even in the years when Queen Elizabeth II was becoming weaker and weaker, and the king was doing more of her duties, there was a sense from William that he had to step up more and more," Hardman continued. "That’s why William and Charles have a good working relationship… If you look back through history, there was usually great tension between the monarch and the heir to the throne — really extraordinary tensions… But that hasn’t happened in modern times."

Queen Elizabeth II, England's longest-reigning monarch, died in September 2022 at age 96. (Dominic Lipinski/WPA Pool/Getty Images)

A source told royal expert Neil Sean that Harry has been feeling "the birthday blues" since he turned 40. On Sept. 30, the father of two attended the annual WellChild Awards in London, the charity he has continued to champion since stepping back as a senior royal.

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Prince Harry, Duke of Sussex smiles as he attends the WellChild Awards 2024 at the Royal Lancaster Hotel  in London on Sept. 30. WellChild is a national charity supporting seriously ill children and their families. (Chris Jackson/Getty Images)

"Harry was keen to get some opinion on exactly where he stands within the U.K. market and admitted to my source that he had birthday blues about hitting 40, but also added that he was excited about the next decade," Sean told Fox News Digital. "The source described his reasoning as being "basically nobody knows where life is taking them, right?’"

The insider told Sean that the prince "…admitted that he adores the WellChild Awards simply because it makes him rethink his life — whatever problems he thinks he’s got, it's simply nothing compared to what these brave children go through." The source noted that Harry "misses the U.K. on a day-to-day basis."

The source claimed to Sean that Harry would consider coming back to live in London full-time again if he had it his way, but "once you have children, your life is no longer your own."

The Duke and Duchess of Sussex share two young children — Prince Archie, 5, and Princess Lilibet, 3. They are being raised in California.

Prince Harry has been the charity's patron since 2007 and has attended its awards ceremony 12 times. (Yui Mok/PA Images via Getty Images)

"Further along in the conversation he asked me whether I’d had the opportunity to read his autobiography and had that changed my opinion about him," the source told Sean. "He seemed really eager for this particular line of questioning — it turned out I wasn’t the only one that he mentioned it to. When he left, he was all smiles and upbeat and positive."

"I got the feeling that… his life was not fulfilled as he’d like to portray," the source continued. "But one has to say, he made every single one of those children in that room at that hotel feel incredibly special and for that, all of us should be grateful."

Sean believes that Harry "wants to come back" to his home country, but the people he needs to convince are "his family — the royal family."

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Sources claimed to People magazine that King Charles stopped responding to Prince Harry's phone calls and letters. (Chris Jackson/Getty Images)

Hardman previously claimed to Fox News Digital that Charles had been urged not to answer Harry's calls and messages to keep his "stress levels down."

"I know people keep saying, ‘Why doesn’t he see Harry when he is in town? Why can’t they patch things up?’ Hardman explained. "But right now, there is a sense that we’ve just got to keep the king’s stress levels down. We don’t want him to have extra things to worry about. Let’s get through this… There is a sense that now is probably not the time."

"If you listen to what Harry has said in his TV series, in his book, in interviews — there’s a lot to unpack," Hardman shared. "There are a lot of things he wants to get sorted out to go through to process… Right now, there’s a sense that it’s not the time. But I’m sure the king would like to normalize things."

Robert Hardman's book, "The Making of a King: King Charles III and the Modern Monarchy," is available now. (Pegasus Books)

A Buckingham Palace spokesperson didn’t immediately respond to Fox News Digital’s request for comment.

Harry has had a strained relationship with his family since he and his wife quit royal duties in 2020. At the time, the couple said the unbearable intrusions and racist attitudes of the British press were what prompted them to step back as senior royals.

"Spare" was published in January 2023. (Justin Tallis/AFP via Getty Images)

The father of two has since detailed his rocky relationship with his family in TV interviews, a documentary and his memoir, "Spare."

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The Duke and Duchess of Sussex spoke to Oprah Winfrey in 2021, a year after they made their royal exit. (Getty Images)

In March 2021, Harry told Oprah Winfrey in a televised interview that the king stopped taking his phone calls shortly before he and his wife made their royal exit.

A friend of the couple claimed to People magazine that safety was always a primary concern for the prince, along with a lack of support from the palace.

In July, insiders told the outlet that Harry is preparing to appeal a court ruling that upheld the decision to deny him security. The Duke of Sussex wants to reinstate his security to allow more flexible visits to the U.K. for himself, his wife and their two children.

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The sources claimed that the issue plays "a crucial role" in Harry’s ongoing estrangement from his father. 

Harry lost his taxpayer-funded personal protective security after he gave up his status as a working member of the royal family.

"[They] didn’t feel they had a choice," the pal told the outlet. "The only option was to leave — for their sanity. I do think they thought if they got out of this bubble, there would be less focus on them."

Prince Harry is seen here departing in his chauffeur-driven Range Rover after attending the WellChild Awards 2024 at the Royal Lancaster Hotel in London on Sept. 30. (Max Mumby/Indigo/Getty Images)

According to the outlet, some close to the palace hinted that Harry’s memoir and interviews have compromised the family’s trust in him. Meanwhile, those close to the prince argued that if he had proper security, he wouldn’t need to speak publicly to help pay for it.

If the issue over security is resolved, "it’s swords down," claimed the friend.

"[Nothing] would give [Harry] more happiness than being able to rekindle his bond with his father," the pal told the outlet. "At the end of the day, you can’t undo bloodlines. He’s not asking his dad for a nicer house or nicer cars. He’s asking because of the reality of the situation. He is at risk."