Since he was born back in 1982, Prince William's whole life has been mapped out for him.
As an heir to the throne, one day he will become King and has been aware of his future from a young age.
But one royal expert has said that his mother Princess Diana actually thought William's younger brother Prince Harry would actually make a better monarch, so much so that she even had a secret nickname for him, writes The Mirror.
But the late princess never revealed the reason why she thought her youngest son would be a better fit for the job of King.
But it has been claimed that William often confided in her that "he didn’t want to be king”.
And in reply, a young Harry is said to have declared: "If you don’t want the job I’ll have it."
According to royal expert Robert Jobson, this led to Diana privately calling Harry GKH - or Good King Harry.
He told the Channel 5 programme William & Harry: Princes At War?: “She used to refer to Harry as GKH (Good King Harry) because she thought he’d probably be better equipped for the role in the future than William.”
Meanwhile, TV broadcaster Jeremy Paxman also said Diana talked about her sons' futures during a lunch meeting.
He explained: "We talked about our children and she said William often told her that he didn’t really want to be king, and then Harry would say, ‘If you don’t want the job I’ll have it'."
In 1995, during her famous Panorama interview with Martin Bashir, the princess was asked if the title of King should go directly to William, who was then aged 13.
She said: 'Well, then you have to see that William’s very young at the moment, so do you want a burden like that to be put on his shoulders at such an age? So I can’t answer that question.”
However, with William now just months away from his 40th birthday, one royal expert has said she believes he is now matured into his future royal role.
Speaking to OK! former royal correspondent Jennie Bond said: "She [Diana] said that he found at that age, in his early teens, the burden of kingship was already weighing quite heavily on his shoulders.
"I think we did see a reluctance to take on the role earlier on, in his early adolescence, he knew his destiny as none of the rest of us do from such an early age."
"But in the last couple of years, he has shown convincingly that he is the man for the role and that he cares about being king.
"He absolutely fully accepts the role and the responsibility destiny has put his way."
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