Few famous Britons, it seems, can resist the chance to be painted by Jonathan Yeo. David Attenborough, the 97-year-old broadcasting legend, is among those who have recently climbed the spiral stairs to his snug studio, hidden at the end of a lane in West London, to pose for Mr. Yeo, one of Britain’s most recognized portrait artists.

Yet when it came to painting his latest portrait, of King Charles III, the artist had to go to the subject.

Mr. Yeo rented a truck to transport his 7.5-by-5.5-foot canvas to the king’s London residence, Clarence House. There, he erected a platform so he could apply the final brushstrokes to the strikingly contemporary portrait, which depicts a uniformed Charles against an ethereal background.

The painting, which will be unveiled at Buckingham Palace in mid-May, is the first large-scale rendering of Charles since he became king. It will likely reconfirm Mr. Yeo’s status as the go-to portraitist of his generation for Britain’s great and good, as well as for actors, writers, businesspeople, and celebrities from around the world. His privately commissioned works can fetch around $500,000 each.

Painting the king’s portrait also marks a return to normalcy for Mr. Yeo, 53, who suffered a near-fatal heart attack last year that he attributes to the lingering effects of cancer in his early 20s. The parallel with his subject is not lost on him: Charles, 75, announced in February that he had been diagnosed with cancer, just 18 months into his reign.

Mr. Yeo said he did not learn of the king’s illness until after he had completed the painting. If anything, his depiction is of a vigorous, commanding monarch. But it gave Mr. Yeo deeper empathy for a man he got to know over four sittings, beginning in June 2021, when Charles was still the Prince of Wales and continuing after the death of his mother, Queen Elizabeth II, and his coronation last May.

“You see physical changes in people, depending on how things are going,” Mr. Yeo said in his studio, where he had decorously turned the still-unveiled painting away from the gaze of curious visitors. “Age and experience were suiting him,” he said. “His demeanor definitely changed after he became king.”

The portrait was commissioned by the Worshipful Company of Drapers, a medieval guild of wool and cloth merchants that is now a philanthropy. It will hang in Drapers’ Hall, the company’s baronial quarters in London’s financial district, which has a gallery of monarchs from King George III to Queen Victoria. Mr. Yeo’s Charles will add a contemporary jolt to that classical lineup.

“What Jonny has succeeding in doing is combining the elusive quality of majesty with an edginess,” said Philip Mould, a friend and art historian who has seen the painting and called it “something of a unicorn.”

Mr. Yeo is no stranger to depicting royals. He painted Charles’ wife, Queen Camilla, whom he said was a delight, and his father, Prince Philip, who was less so. “He was a bit of a caged tiger,” Mr. Yeo recalled. “I can’t imagine he was easy as a father, but he was entertaining as a subject.”

Still, a sitting monarch was a first for Mr. Yeo, whose subjects have included prime ministers (Tony Blair and David Cameron), actors (Dennis Hopper and Nicole Kidman), artists (Damien Hirst), moguls (Rupert Murdoch) and activists (Malala Yousafzai).

Mr. Yeo said there was an element of “futurology” to his work. Some of his subjects have gone on to greater renown after he painted them; others have faded. A few, like Kevin Spacey, who was tried and acquitted on charges of sexual misconduct, have fallen into disrepute. The National Portrait Gallery in Washington returned Mr. Yeo’s Spacey portrait, made when the actor played a ruthless politician in the series “House of Cards.”

Gazing back over his A-list subjects, Mr. Yeo has developed a few rules of thumb about his art. Older faces are easier to capture than younger ones because they are more lived in. The best portraits capture visual characteristics that remain relevant even as the person ages. And the only bad subjects are boring ones.

“He didn’t want me to pose, he just wanted me to talk,” said Giancarlo Esposito, the American actor known for playing elegant villains in the crime classic “Breaking Bad” and the recent Guy Ritchie TV series, “The Gentlemen.” As an actor, Mr. Esposito said, he was skilled at projecting a persona, “but there was no way to fool him.”

“It was an opportunity to be Giancarlo, unmasked,” said Mr. Esposito, who said he last posed for a portrait as a child at a county fair.

A loose-limbed figure with a quick smile and stylish eyeglasses pushed far back on his forehead, Mr. Yeo learned his appreciation for the charms and foibles of public figures by being the son of one. His father, Tim Yeo, was a Conservative member of Parliament and minister under Prime Minister John Major, whose career was undone by professional and personal scandals.

At first, the elder Mr. Yeo had little patience for his son’s artistic dreams. “My dad definitely assumed I’d need to get a proper job,” he said, giving him no money when he took a year off after high school to try to make it as a painter. Mr. Yeo’s early efforts showed his lack of formal training, and “obviously, I didn’t sell any pictures.”

Then, in 1993, at the end of his second year at university in Kent, he was struck by Hodgkin’s disease. Mr. Yeo burrowed deeper into painting as a way of coping with the disease. He got a break when a friend of his father — Trevor Huddleston, an Anglican archbishop and anti-apartheid activist — commissioned him for a portrait.

“He asked me mostly out of pity,” Mr. Yeo recalled. “But it turned out spectacularly, better than anyone expected.”

The commissions began to flow, and Mr. Yeo became sought-after for his revealing portraits of famous faces. In 2013, the National Portrait Gallery in London mounted a midcareer exhibition of his work.

“He brought the portrait back,” said Nick Jones, the founder of Soho House, a chain of private members’ clubs, which worked with Mr. Yeo to hang paintings by him and other artists on its walls. “Portraits were always such severe things,” Mr. Jones said. ”He was able to add layers and bring out the personality of the people.”

It helps that Mr. Yeo is well-connected, prolific and entrepreneurial. He is cleareyed about the commercial side of his art. “No matter how you dress it up,” he said, “to some extent, you’re in the luxury goods business.”

Successful but creatively restless, Mr. Yeo began experimenting. When aides to President George W. Bush contacted him to do a portrait and later dropped the project, he decided to do it anyway, but as a collage of images cut out of pornographic magazines.

The Bush portrait went viral on the web, and Mr. Yeo created collages of other public figures, including Hugh Hefner and Silvio Berlusconi. It was provocative but time-consuming work — he bought stacks of skin magazines to assemble enough raw material — and his supply dried up when, he said, “the iPad killed the porn-magazine industry.”

Mr. Yeo also became drawn to the uses of technology in art. He worked on design projects at Apple. He painted the celebrity chef, Jamie Oliver, via FaceTime during the pandemic. And he created an app that offers a virtual-reality tour of his studio, a well-appointed space in an old workshop that once turned out organs.

But on a Sunday night in March 2023, Mr. Yeo’s busy life came to a terrifying halt. He went into cardiac arrest — his heart stopping for more than two minutes. Mr. Yeo said he believes the crisis was linked to his cancer treatment decades earlier. While he did not see a bright light at the end of a tunnel, as others with near-death experiences have described, he recalled a palpable sensation of floating outside his body.

Mr. Yeo, who is married and has two daughters, clung to life. After recuperating, he found that his vocation as a painter — temporarily diverted by his detours into technology and other pursuits — had been rekindled. Soon, he was immersed in the portraits of Charles, Mr. Esposito and Mr. Attenborough.

“It definitely makes you feel, ‘Let’s not mess around anymore,’” Mr. Yeo said. “It’s like dodging a bullet.”