Throughout his long wait to ascend the throne, King Charles stood out for his outspoken views on everything from climate change to architecture. Now he is monarch, the 73-year-old may try to keep his cards close to his chest.
Ridiculed by some for his opinions, and accused of meddling in political and social matters that may not concern him, Charles has always believed he should be able to speak his mind on issues which he feels are important to Britons too.
But Charles has said he was aware that heir-to-the-throne and monarch were two very different roles.
In a TV documentary to mark his 70th birthday in 2018, Charles sought to quell fears that he would use his position to promote his favourite causes.
"The idea, somehow, that I'm going to go on in exactly the same way, if I have to succeed, is complete nonsense because the two - the two situations - are completely different," he said.
Asked whether his public campaigning would continue when king, he said: "No, it won't. I'm not that stupid."
That change may not be so simple.
For years, Charles has found himself straddling the more traditional style of monarchy which his mother adhered to and under which he was raised, with a more modern, approachable version which his son, and now heir, Prince William personifies.
That leaves a contradiction between him pursuing socially liberal causes on one hand, while being intrinsically conservative on the other, a dichotomy some commentators warn could prove difficult for Charles and the public.
Journalist Catharine Meyer said in a 2015 biography that royal courtiers were concerned Charles would pursue a radical style of monarchy and that his passion for certain causes, particularly environmental, had caused disquiet at Buckingham Palace, and with the late Queen Elizabeth herself.
"Some courtiers — and the sovereign herself — fear that neither the Crown nor its subjects will tolerate the shock of the new," Mayer wrote.
"They feel he puts his more cerebral passions — his activism — before his royal job. They are a long way from being persuaded of Charles's evolving view: that campaigning and kingship can be synthesised."
Under Britain's unwritten constitution, the royal family is supposed to remain above politics and Elizabeth kept her opinions to herself during her reign of more than seven decades.
"I have no idea what her actual politics (are) and I was prime minister for 10 years," said Tony Blair, prime minister from 1997 to 2007.
AHEAD OF HIS TIME?
For five decades, Charles has campaigned for subjects close to his heart, garnering both praise and opprobrium.
The new king's supporters say he is a man ahead of his time who thinks deeply about his subjects and wants to use his role to highlight important issues.
Critics argue his position has meant people have pandered to his views, some of which they do not agree with.
He himself has acknowledged that raising unfashionable ideas such as climate change, decades before world leaders put it centre stage, had led some to accuse him of being an "idiot".
"I minded about balance and harmony," Charles told the BBC about his environmental concerns, saying the criticism "wasn't much fun".
"Because I suggested that there were better ways of doing things in the nicest possible way, and a more balanced and integrated way, I was accused of interfering and meddling."
One of his greatest personal achievements was creating the Prince's Trust, a charity to help young Britons get skills and training to find jobs or start businesses.
Set up around the time of riots across the country and amid a rising unemployment crisis, it has since helped more than one million people. Charles said it would have been criminally negligent of him to ignore such issues.
"If it's meddling to worry about the inner cities as I did 40 years ago, then if that's meddling I'm proud of it," he said.
He has spoken out about architecture, antagonising some within the industry with his open dislike of many modern buildings and designs.
He famously described an extension to London's National Gallery in 1984 as a "monstrous carbuncle on the face of a much-loved and elegant friend".
He put his own ideas into practice in Poundbury, an urban extension to the mediaeval town of Dorchester in southwest England on 400 acres of land owned by his Duchy of Cornwall based on traditional town planning principles he advocated.
Critics say the project, which he started in 1987 and is due to be completed in 2025, is a fantasy throwback. Supporters and many of its residents say it is radical and successful.
His advocacy of alternative medicines and therapies has been equally derided.
"Prince Charles contributes to the ill-health of the nation by pretending we can all over-indulge, then take his tincture and be fine again," said Edzard Ernst, a former professor of complementary medicine at Exeter University, in 2009.
"Under the banner of holistic and integrative healthcare he thus promotes a 'quick fix' and outright quackery."
But it is his passion for environmental issues and organic farming produce, founding the Duchy Originals brand to promote organic food, that have been his main preoccupation.
A farmer himself, Charles is patron of the Soil Association, and in 2010 he wrote a book with advisers called "Harmony: A New Way of Looking at Our World".
He has championed sustainability and in recent years warned that problems caused by climate change were fuelling wars, terrorism and mass migrations. He himself acknowledged his views have courted controversy.
"The trouble is in all these areas, I have been challenging the accepted wisdom, the current orthodoxy and conventional way of thinking," Charles said.
"Perhaps I should not have been surprised that so many people failed to fathom what I was doing. So many appeared to think or were told that I was merely leaping from one subject to another from architecture one minute to agriculture the next.
"What I have actually been trying to demonstrate is that all these subjects are completely interrelated and we have to look at the whole picture to understand the problems we face."
It is not just his views that have caused concern, but also his attempts to raise issues with the government of the day. In 2013, it was revealed Charles had held 36 meetings with government ministers in the previous three years.
Two years later, Britain's top court ruled that more than 40 letters to and from Charles or his aides to ministers - dubbed the "black spider memos" because of the prince's scrawled handwriting - could be released.
Topics ranged from affordable rural housing, the quality of food in hospitals and the preservation of historic buildings to resources for British troops in Iraq and the fate of the Patagonian Toothfish.
As recently as June this year, Charles provoked a backlash from ministers after it was reported he had criticised a government policy to send asylum seekers to Rwanda.
"Prince Charles is an adornment to our public life, but that will cease to be charming if he attempts to behave the same way when he is king," an unnamed senior minister told the Times. "That will present serious constitutional issues."
In 2014, Charles also caused a diplomatic row when private comments in which he reportedly likened Russian President Vladimir Putin to Adolf Hitler following Russia's annexation of Crimea were made public.
"He has a view of the world and he wants to impose his view of that world, so in every way he doesn't want to conform to expectations, so that makes him a rebel," said Tom Bower, who wrote a biography of Charles to coincide with his 70th birthday.
"I think that if he's a rebel king, the monarchy will be in danger."
In his new role, Charles will hold weekly private audiences with the prime minister where they discuss government matters.
Whether his interventions into political matters stray further than that is what royal aides are holding their breath to discover, media reports of inner royal circles say.
"His role will alter when he becomes sovereign. Then, he is bound by the conventions relating to advice. His speeches and acts are then those of his ministers. It is, I think, absurd to think he is unaware of this," constitutional historian Professor Vernon Bogdanor said in a 2017 lecture.
Republic, a group that campaigns for the abolition of the monarchy, says it has a simple message for the new king.
"If Charles wants to be involved in politics, stand for election," it says.
Charles's former private secretary William Nye said the new king would follow the example of his mother and grandfather George VI, while drawing on his own experiences.
However, Charles himself has suggested there are some issues about which he will refuse to be silenced.
"You are accused of being controversial just because you are trying to draw attention to things that aren't necessarily part of the conventional viewpoint," Charles said in a magazine interview to mark his 70th birthday.
"My problem is I find there are too many things that need doing or battling on behalf of."