King Charles III has proved to be a smart monarch with his bombshell decision to secure the future of the royal family.

After being diagnosed with ­cancer, the 75-year-old decided to take a bold step to save the monarchy and the royal family.

A royal aide said: “The monarch chose the family’s safety over William’s anger as he convinced the heir to sacrifice for the late Queen’s legacy.”

“Future King William and his family finally gave in to the monarch’s decision and agreed to stop flying together,” confirmed the insider.

It comes after a passage form Robert Jobson’s soon-to-be released book , published by the Mail Online, which reads: “It would be scant consolation, of course, for an unspeakable tragedy, let alone for the prospect of King Harry and Queen Meghan…”

“King Charles, perhaps reminded of his own mortality, echoed his late mother’s concerns,” according to the royal biographer.

The insider did not confirm whether the father-son due signed a formal ­document in this regard.

 However, Jobson claimed in his biography, which is set to hit shelves on August 1st, that there was a formal agreement between the royals.