Breaking:Here The Real Reason Prince Harry and King Charles Are No Longer Speaking: ‘Harry’s Calls Go Unanswered’ (Exclusive)

Prince Harry’s desperation to protect his wife and kids has deepened his estrangement from his father, King Charles.

When the Duke of Sussex, 39, returned to the U.K. in May to celebrate the 10th anniversary of one of his proudest achievements, the Invictus Games, his father was notably absent from the ceremony.

The two were unable to meet during Harry’s visit, which the prince’s spokesperson attributed to the King’s “full schedule.” However, sources close to Harry suggest a deeper issue. Harry wanted to discuss his ongoing battle for security, which he has been fighting for in court for more than four years and believes Charles, 75, has the power to reinstate. (Buckingham Palace will not comment on security provisions, but a palace source tells PEOPLE the notion that Harry’s security is in Charles’s hands is “wholly incorrect.”)

The family rift that first became public in 2020 when Harry and his wife, Meghan Markle, stepped back from their royal roles has been marked by blistering attacks and unresolved tensions. But for Harry, no single issue is a greater sticking point than that of security, multiple well-placed insiders in his circle tell PEOPLE in this week’s exclusive cover story.

Despite a positive meeting between the father and son in February following the King’s cancer diagnosis, their communication has since deteriorated. Those close to Prince Harry say the monarch no longer takes his son’s calls or responds to his letters.

“He gets ‘unavailable right now,’ ” says a friend of Harry’s. “His calls go unanswered. He has tried to reach out about the King’s health, but those calls go unanswered too.”

Amid the estrangement, Prince Harry remains deeply concerned for the safety of his wife and children, Prince Archie and Princess Lilibet, and has, according to sources, repeatedly asked his father for help.

“Harry is frightened and feels the only person who can do anything about it is his father,” a royal insider tells PEOPLE. Another source close to the situation says, “Harry is determined to protect his own family at all costs.”

Now the fight is boiling over. In the ITV documentary Tabloids on Trial, which aired in the U.K. on July 25, Prince Harry voiced his fears that negative press could provoke a violent attack on his wife.

“All it takes is one lone actor,” he said, citing these “genuine concerns” as his reason for not bringing Meghan, 42, Archie, 5, and Lilibet, 3, back to the U.K.

The Duke of Sussex has also taken the battle to the courts, where he lost his bid to restore his taxpayer-funded security earlier this year. (He has plans to appeal.)

Exactly what is stopping Harry from securing the protection he seeks is a matter of bitter contention. Constitutionally, the monarch has no governmental power in the U.K., and the power to bestow police protection lies with the Executive Committee for the Protection of Royalty and Public Figures (RAVEC), which operates on behalf of the U.K. government.

But Harry, whose offer to personally cover the cost of police protection was also rejected in court, feels that as King, Charles could intervene to ensure such protection is extended.

The issue has created an impenetrable wall between Harry and Charles. The conversation has now shifted from frustration to “complete silence” from the King, claims the friend.

Sources close to the Duke and Duchess of Sussex, who have established a new life in Montecito, California, say the palace is mindful of what happened when Princess Diana left royal life — and instantly eclipsed the institution.

“Charles’ fear is a repeat of the past,” the insider says. “When his wife divorced the institution, she took the headlines, overshadowed his work and became a global superstar. Seeing his son leave with his wife was not part of the plan.”

Safety has always been a cornerstone of why Meghan and Harry say they decided to leave. The Duchess of Sussex has cited negative press and the lack of royal support during her time as a working royal as reasons she contemplated suicide.

The couple “didn’t feel they had a choice,” says the friend. “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.”

The Queen made it clear that effective security was necessary due to the threats against them, but somewhere along the line there was interference,” the royal insider alleges.

The security downgrade was ultimately enacted by RAVEC. Its membership includes the Home Office (the U.K. version of Homeland Security), the Metropolitan Police and the Royal Household. Although the King has no direct involvement with RAVEC, his staff sits on the committee. A government spokesperson says they provide “rigorous and proportionate” security and do not disclose details “as doing so could compromise their integrity and affect individuals’ security.”