Volkswacht Bodensee - Gun salutes for King Charles III as he marks 77th birthday

Gun salutes rang out in London to formally mark the occasion, while the monarch inaugurated a train depot in the rain in south Wales.

Charles also attended a reception with Queen Camilla for the 200th anniversary of Cyfarthfa Castle, considered a Welsh historical jewel.

Charles has maintained a relatively busy schedule of royal duties since his return to public life following the announcement of his diagnosis with an unspecified form of cancer in February 2024.

He resumed public facing engagements a few months later with a visit to a London cancer treatment centre, where he met fellow sufferers and spoke of the "shock" of receiving a cancer diagnosis.

Since then he has kept up a steady stream of royal duties including hosting a pomp-filled state visit by US President Donald Trump at Windsor Castle in September.

- 'Living with cancer' -

While most of his engagements are confined to the United Kingdom, Charles has made some foreign trips.

Last month, the royal couple visited the Vatican, when Charles held a landmark joint prayer session with Pope Leo XIV.

"What they say is 'he's living with cancer'. They don't say anything other than that. We can't know any more than that," said royal author Robert Jobson.

"It's not the same as he is in remission... But I think he's doing a terrific job of what he's doing," he said, adding that he could not be expected to be "100 percent fit".

Charles has a reputation as something of a workaholic and is said to have been eager to get back to work quickly.

Some habits have altered however: the monarch has reportedly been persuaded to change the habit of a lifetime and now eats lunch.

Camilla, speaking to the BBC while visiting the Vatican, said Charles loved his work and that it "keeps him going".

"If you've been ill and you are recovering, you're getting better and now he wants to do more and more and more. That's the problem," she said.

- Andrew headache -

Charles' return to work may have gone smoothly but managing other members of what the late Queen Elizabeth II famously called "the firm" has proved a headache.

Already reeling from a highly publicised rift with his younger son Harry, he has faced more controversy surrounding his brother Andrew.

Charles last month stripped Andrew of his prince title in an attempt to limit the damage to the monarchy of the scandal of his brother's links to convicted US sex offender Jeffrey Epstein.

As part of the sanction, Andrew was also told he could no longer live in his palatial home on the royal family's Windsor estate west of London.

But with material linked to Epstein still being released and picked over in the United States, stripping Andrew of his title is unlikely to be the end of the affair.

While Charles continues his treatment, other members of the family are becoming more prominent.

Heir and future king Prince William made his first visit to Brazil this month for his annual Earthshot Prize which awards one million pounds ($1.3 million) to five pioneering projects tackling threats to the environment.

A committed environmentalist like his father, he has made it clear he wishes to make time to dedicate to his family -- wife Catherine and children George, 12, Charlotte, 10, and Louis, seven.

But he also said in a recent interview that "change is on my agenda".

R.Flueckiger--VB