Lucian Freud’s final portrait is of a naked man and a dog. It is unfinished but otherwise betrays no sign of the agedness of its creator, who died last July 20, halfway through his 89th year. The scale is big, a square canvas of about five feet by five feet, and the brushwork is as sure and layered as in any painting he had ever done—smooth and free around the man’s shoulders, crusty and impastoed along the arms. The palette is Caucasian-fleshy from afar but remarkably varied and intricate up close: purples and greens in the man’s legs, vivid streaks of yellow in his right hand, rust and blue at the naughty bits.

For the last 57 years of his life, Freud painted standing up rather than sitting down; the physical restrictions of seated painting, he said, had begun getting him “more and more agitated” in the 1950s, so he kicked the chair away. Painting on his feet required extraordinary stamina, given Freud’s self-imposed work schedule: a morning session with one model, an afternoon break, and an evening session with another model, seven days a week, all year round. What’s more, these sessions had a tendency to stretch on: a deliberate worker, Freud took 6, 12, 18 months or longer to complete a painting, marathoning into the night if the mood struck. But he had stamina in spades. Painting was his workout; he took no other exercise, and yet photographs of him working shirtless in 2005, when he was 82, show him to be lean and all sinew, a jockey-size Iggy Pop.

But by June 2011, Freud recognized that his body was finally failing him, and that he had only so many brushstrokes left. The naked man in the portrait was completed, but the dog, a tan-and-white whippet, would never get its hind legs. Freud prioritized its head and face, adding a little dart of terre verte (“green earth”) mixed with umber to depict the tip of the animal’s pricked-up right ear. In early July, Freud was addressing the painting’s foreground: the folds and ripples in the sheet that covered the low platform upon which his two models sprawled. Here and there, as his energy permitted, he applied quick strokes of flake white, a thick, lead-heavy paint, to the lower part of the canvas.

That was as far as he got. Able to stand no longer, he at last retired to his bedroom, one floor up from the studio he kept in his Georgian town house in West London. As he lay in bed, friends and family gathered to pay their respects. There were many visitors from both categories. Freud had an otherworldly magnetism that his intimates struggle to put into words. Deborah Cavendish, the Dowager Duchess of Devonshire, once ascribed to him “a sort of starry quality … an extraordinary sort of mercurial thing. He’s like something not quite like a human being, more like a will-o’-the-wisp.” Over the course of his life he fathered 14 acknowledged children with six women. Among his nine daughters are the fashion designer Bella Freud and the novelist Esther Freud. Two weeks into their bedside vigil, he was gone.

Freud’s was not one of those postscript deaths, the final headline in a life that had long ago ceased to matter or progress. It was an interruption—the ultimate inconvenience for a man who still had plenty of work to do and plenty of people who wanted to see his work. The restaurateur Jeremy King, who was more than a hundred sittings into an uncompleted etching when Freud died—having already sat for a painting completed in 2007—recalls that the artist “never came to terms with the fact that he was slowing down. He constantly said, ‘What’s wrong with me?’ And I’d say, ‘Well, Lucian, you’re actually much more active than any other 68-year-old I know, let alone 88.’ And the moment he lifted his hands, most of his ailments seemed to melt away. The concentration and the adrenaline pushed him through.”

From his mid-60s onward, the pinochle years for most men his age, Freud had been enjoying a fruitful and vigorous late period. This wasn’t a function of critical recognition, though it happened to be in this period that critical favor finally smiled upon him, with *Time’*s Robert Hughes judging him “the best realist painter alive,” a sobriquet that stuck. Nor was it a matter of commercial success, though it was in 2008 that Freud’s Benefits Supervisor Sleeping (1995) fetched the highest-ever auction price for a painting by a living artist, selling at Christie’s to the Russian petrogarch Roman Abramovich for $33.6 million.

Freud simply did great work as an old man, some of his greatest. “In a sense, I think he knew this was his last big push at making some remarkable works. I could just see that he was really ambitious, pushing as hard as he could,” says the naked man in that final painting, David Dawson, the artist’s longtime assistant and the owner of Eli, the whippet star of several late paintings. (Freud had bestowed the dog upon Dawson as a Christmas present in 2000.) When Dawson started working for Freud, 20 years ago, the artist was in the middle of a series of nudes of the drag performer and demimonde fixture Leigh Bowery. Bowery was a huge man, lengthwise and girthwise, with a bald, oblong head—a lot to work with in terms of topography, physiognomy, and epidermal hectarage. Yet Freud went bigger still, painting Bowery larger than life-size. Freud had his canvases extended northward, eastward, and westward as it suited him; often, he would work the upper reaches of a painting from atop a set of portable steps.

An Island upon an Island

There were lots of big paintings in this late period: not just of Bowery and his clubgoing friend Sue Tilley, the heavyset welfare-agent-by-day of Benefits Supervisor Sleeping, but of more ordinarily proportioned people, such as Freud’s military-officer friend Andrew Parker Bowles. The seven-foot-tall portrait of Parker Bowles, The Brigadier, painted over 18 months of sittings between 2003 and 2004, was a playful experiment: Freud dispensing with his usual propensity for exposed flesh to do a Reynolds- or Gainsborough-style painting of a distinguished British gentleman in uniform—albeit with a characteristically lumpy, earthy, Freudian twist. “Lucian asked to paint me in the uniform I wore when I was a commander of the Household Cavalry,” says Parker Bowles, the former husband of Camilla and a former Silver Stick in Waiting to the Queen. “But it had been 20 years since I’d worn it, and I’d got fatter. So I undid my tunic and my stomach came out.”

The painting is magnificent—melancholy and funny at the same time: a military man resplendent in his beribboned coat with a gold-braid collar and his smart dark trousers with wide red stripes down the side, but with his face lost in thought (nostalgia? regret? ennui?) and his midsection asserting itself as the picture’s focal point. The placket down the middle of Parker Bowles’s white shirt divides his gut into two testicular bulges. “When I look in the mirror, I think, Not bad, but then I see the painting and hear people say things like ‘It shows the decline of the British Empire,’ ” says Parker Bowles. “Well, so be it.”

In addition to tackling the big canvases, Freud resumed making etchings late in life, returning to a form he’d left behind in his youth. He took on his share of small paintings, too, such as his neck-up portraits of King, David Hockney (2002), and a distinctly Broderick Crawford-resembling Queen Elizabeth II (2001).

At the time of his death, Freud was not only partway through the etching of King, whose restaurant the Wolseley he dined in several nights a week, but also well into his second painted portrait of Sally Clarke, whose restaurant-café, Clarke’s, a Notting Hill institution just down the road from his house, was where he took his breakfast and lunch nearly every day.

This overdrive work ethic was at once an acknowledgment of pending mortality and a hedge against it. Dawson marvels at what his boss managed to achieve. “The sheer volume, the scale,” he says. “He never rushed the work. But, my God, one great painting after another came out. He felt he could do it and he was able to. And this was his last chance.”

Despite standing only about five feet six, Freud was an imposing figure, with a fierce gaze often likened to a hawk’s, and a severe, aristocratic mien; even when painting, he always wore a long scarf, rakishly knotted at the neck. He was also an intensely private man who didn’t want his biography to inform people’s reception of his art. That he was the middle son of the youngest son of Sigmund Freud; that he had been born in 1922 in Berlin and moved with his family to England in 1933, the year Hitler became chancellor of Germany; that his acquaintances over the course of his life ran the gamut from Pablo Picasso to Alberto Giacometti to the Duke of Beaufort to the gangster Kray twins to Kate Moss; that he was a ladies’ man and an inveterate horseplayer—all irrelevant. An artist, he said, should appear in his work “no more than God in nature. The man is nothing; the work is everything.”

And, fair enough, one needn’t know anything about Freud to appreciate his pictures. Consider his mastery, in paintings ranging from Pregnant Girl (1960–61) to Naked Girl with Egg (1980–81) to Woman Holding Her Thumb (1992) to Naked Portrait (2004–5), of how bosoms sag and pool atop a recumbent woman’s chest—an unidealized view of womanhood that’s nevertheless almost feminist in its resistance to prescribed expectations of lady portraiture. Or consider the hyper-masculine whomp delivered by Head of a Big Man (1975), its middle-aged sitter’s florid, meaty noggin rising menacingly out of a pale-blue dress shirt like the head of a cranky tortoise out of its shell. These images may be unsparing, but they are not, as Freud’s detractors and even some of his admirers say, cruel and/or grotesque. Rather, they are intensive engagements with his models as living creatures, what their heads and bodies are like as blood, oxygen, and emotion circulate through them. They’re fun, amazing pictures to get lost in.

This year, two major retrospectives will give the British and American public an unprecedented opportunity for full-on Freud immersion. On February 9 the National Portrait Gallery’s exhibition “Lucian Freud Portraits” opens in London as part of the city’s Cultural Olympiad run-up to the Summer Olympic Games. Featuring more than 130 pieces, it is the first Freud retrospective devoted exclusively to his depictions of people, and the artist was personally involved in its preparation—although, says the museum’s curator of contemporary art, Sarah Howgate, “He did say, ‘Well, I won’t be around in 2012.’ ” The “Portraits” show will move to Texas this summer, opening at the Modern Art Museum of Fort Worth on the second of July. And on February 17 the Blain/Southern gallery, in London, will unveil “Lucian Freud: Drawings,” the most comprehensive survey ever of Freud’s works on paper, presenting more than a hundred drawings and etchings from the 1940s to the near present. The “Drawings” retrospective will be at Blain/Southern through April 5 and then at Acquavella Galleries, in New York, from April 30 through the ninth of June.

It was with the National Portrait Gallery exhibition in mind that Freud dedicated himself to getting as far as he could on Portrait of the Hound, as the square painting of Dawson and Eli has come to be known. He had spent much of his career being deeply unfashionable, a figurative artist besotted with Constable and Titian as the midcentury world around him went Abstract Expressionist, Op, and Pop. Not that this ever seemed to affect him. While others in his cohort—such as the artist-illustrator John Minton, who was the subject of a gloomy, arresting Freud portrait in 1952 and took his own life in 1957—despaired of their irrelevance, Freud carried on, an island upon an island.

He did, however, undergo one major stylistic shift. His early works are coolly colored, draftsman-precise, and strictly two-dimensional—bereft of the fleshly qualities with which he would come to be identified. His late-40s paintings of his first wife, Kitty Garman, the daughter of the sculptor Sir Jacob Epstein, are wonderful in their own way but seemingly the work of some other artist: her face rendered with a rolling-pinned flatness, and every last frizz of her split-ended hair faithfully documented. But Freud’s friendship with the artist Francis Bacon, which began in the 1940s, prompted him to change his approach: “I think that Francis’s way of painting freely helped me feel more daring,” he said.

The new, free approach proved revelatory, not just to the artist but to his audience. The transitional Woman in a White Shirt, painted in 1956 and ’57, is a good example. Its subject was his friend the Duchess of Devonshire, née Deborah Mitford, the youngest of the Mitford sisters. But her English-rose beauty is hardly evident in the portrait, roiled as it is with swabs and swirls of drab color—“all greenish khaki,” as the now 91-year-old Dowager Duchess writes in her newest memoir, Wait for Me! Yet the wonder of it is, Freud’s painting, in its turbulent strokes and M.R.I.-like scrutiny, foretold the future: “As I have got older,” its subject writes, “so my likeness to the portrait grows.”

Freud’s brushwork would get only freer from there as he swapped out his soft sable brushes for stiff, bristly hog’s-hair ones that he would snip down to nubs. From the 60s forward, the paint got thicker, too—whorled, layered, and smeared as he laboriously built up form through color. Not uncoincidentally, Freud’s paintings became more sensual, increasingly if not exclusively focused on nude bodies.