In 1953, Elizabeth II was crowned at just 25 years old, in an atmosphere of national enthusiasm in a country still recovering from the trauma of the Second World War. She remained a very popular and respected figure throughout her life.
The reception reserved for his eldest son promises to be very different. At 73, it is an "old man" who ascends the throne, notes Robert Hazell, professor of constitutional law at University College London.
"It will be very difficult for him to take over from the queen," he told AFP. "The monarchy will probably go through difficult times."
Born in 1948, Charles married Diana Spencer in 1981, with whom he had two children, William and Harry, before their marriage fell apart and public revelations about their respective infidelities led to their divorce.
After Diana's tragic death in 1997 in a car accident in Paris, chased by paparazzi, Charles in 2005 married his former mistress Camilla Parker Bowles.
The new king has long stood out for his controversial, and sometimes ridiculous, remarks on subjects such as agriculture or modern architecture (which he dislikes). Even if his environmental concerns are now widely shared, he will have to comply with foolproof neutrality, each word of the sovereign being scrutinized and commented on.
In 2018, he assured the BBC that he was aware that he should refrain from taking any position: "I'm not that stupid".
Such neutrality promises to be "very difficult" to maintain, especially in the face of Scotland's desire for independence, while wanting to safeguard the monarchy, notes Mr. Hazell, who nevertheless underlines "the very strong sense of public service and public duty" by Charles.
- Not Elizabeth's "aura" -
Charles approaches his reign much less beloved than his mother. According to a poll by the YouGov institute in 2021, just over a third of respondents thought he would make a good king, while over 70% had a favorable opinion of the queen.
Enough to revive the hopes of supporters of the abolition of the monarchy in favor of a republic, an idea supported by only 15% of Britons in recent years.
Charles "is not protected by the same almost impenetrable aura as the Queen", according to Graham Smith, the director of the Republic movement.
To maintain the institution, Robert Hazell considers "conceivable" that Charles abdicates in favor of his son William, born in 1982 and very popular, an option still rejected by Elizabeth II.
- Reduced lifestyle -
But for Graham Smith, "he's not going to give up".
Faced with growing criticism of the lifestyle of the royal family, scholars of the monarchy lend Charles the desire to reduce the number of its active members, living at the expense of the crown and devoting themselves to public engagements. They are currently ten.
The trend has already been boosted with the withdrawal of Prince Andrew, brother of Charles, implicated for his friendship with the late American financier Jeffrey Epstein, accused of trafficking in minors, then the departure for California of his son Harry.
For Robert Hazell, more than financial, the interest of continuing on this path is above all to limit the risks that a member of the royal family will "slip".
It will be up to Charles to distribute the titles, choosing for example whether he passes on to his son that of "Prince of Wales" which he has worn since 1958.
The royal family has indicated that Camilla should wear the title "princess consort" rather than "queen" so as not to offend the public. But from a legal point of view, notes Mr. Hazell, she became queen "automatically".