While Charles' new role is his birthright, there has been discussion in the past about whether it would be better for the British monarchy for Prince William to become king instead of his father.
One person who spoke about this was Prince William's mother, the late Diana, Princess of Wales.
In her infamous BBC Panorama interview in 1995, the separated princess spoke about the breakdown of her marriage, Charles' affair with Camilla Parker Bowles and how she thought Charles would struggle with the role of king.
Journalist Martin Bashir asked her during the interview if she thought Charles would ever become king.
"I don't think any of us know the answer to that," she replied.
"And obviously, it's a question that's in everybody's head. But who knows, who knows what fate will produce, who knows what circumstances will provoke?" she added, referring to the public reaction to their forthcoming divorce and Charles' relationship with Camilla.
Bashir further probed Diana by asking how Charles felt about being king, to which she replied, "There was always conflict on that subject, with him, when we discussed it and I understood that conflict because it's a very demanding role – being the Prince of Wales – but it's an equally more demanding role being king."
She added that, "being Prince of Wales produces more freedom now and being King would be a little bit more suffocating. And because I know the character, I would think that the top job, as I call it, would bring enormous limitations to him and I don't know whether he could adapt to that."
When she was asked if she would prefer to see her son Prince William succeed Queen Elizabeth II instead of his father, she replied with an enigmatic grin, "My wish is that my husband finds peace of mind and from that follows other things, yes."
Diana's willingness to open up about intimate details of her life rocked the royal family, who since successfully fought to have the Panorama episode banned over the deceptive methods, such as falsifying documents, that the BBC used to convince Diana to take part in the interview.
Princess Diana's opinion on William being a preferable king to Charles after the Queen's death was seemingly confirmed two years ago when a former newspaper editor revealed a conversation he'd had with Diana after she and Charles had split.
"She said that all she cared about was William's succession to the throne," former Daily Telegraph newspaper editor Sir Max Hastings revealed in the documentary Diana: The Truth Behind the Interview.
"She said to me quite explicitly — 'I don't think Charles can do it,'" he added.
"The outcome she wanted to see was for Charles to stand aside as heir to the throne and for William to occupy the throne. This was pretty dynamic stuff."
And when Diana, Princess of Wales died, the public in their anger and grief, seemed to feel the same.
Time has softened people's opinion, however, with the population having warmed to Charles over the years and becoming more accepting of Camilla as Charles' wife and Queen Consort.
"He's 100 per cent ready for this moment. He's clearly the best-prepared monarch we've ever had," Charles's former PR chief Paddy Harverson said on US TV.
"He's the hardest working person I've ever known. I mean that. He never stops. There isn't a day in a year where he isn't working."
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