Coogan's Bluff.(Steve Coogan)

On a sweltering morning in mid-March, three executive producers for HBO's "Curb Your Enthusiasm," David Mandel, Alec Berg, and Jeff Schaffer, lolled around in shorts at the patio table of a Malibu beachfront house waiting for the actors to arrive so that the day's shooting could begin. All were graduates of the Harvard Lampoon and of "Seinfeld." A month earlier, they had put the British comedian and actor Steve Coogan up for the role of Dr. Bright, a psychiatrist whose advice lands Larry (Larry David), the antihero of "Curb Your Enthusiasm," in a world of woe with his wife, Cheryl (Cheryl Hines), in the penultimate episode of the sixth and possibly final season of the series, which airs November 4th. It was a meatier role than most guest appearances, and the producers had been hoping, according to Schaffer, to "get someone great." They were all Coogan fans. Larry David, however, knew nothing about him.

In 2005, "The Comedian's Comedian," a British television special, asked more than three hundred respected comedy professionals worldwide to rank their favorite comedians. Coogan came in at No. 17, just ahead of Charlie Chaplin (No. 18), just behind Peter Sellers (No. 14), and well ahead of many more famous figures, such as Eddie Murphy (No. 32), Bill Cosby (No. 47), and Mel Brooks (No. 50). (Larry David was No. 23.) The forty-two-year-old Coogan is, in some ways, a British version of Larry David. He has captivated British audiences for more than a decade, with a run of enormously successful television series which are the kind of high-water marks of comedy in Britain that "Seinfeld" (for which Larry David co-wrote sixty episodes) and "Curb Your Enthusiasm" are for American viewers.

In his shows, Coogan, like David, has accentuated the negative and explored the comedy of embarrassment. He specializes in creating characters, not jokes. Each comic persona has a distinct world view, a unique idiom, and a richly imagined backstory. Coogan's humor often trades on the almost Oriental complexity of the British class system, which means that his most memorable characters--the beer-swilling Mancunian slacker Paul Calf and his sluttish sister Pauline, for instance--don't always travel well beyond the borders of the British Isles. ("It really bugs me," Paul Calf said in one routine. "They say, 'Oh, David Beckham--he's not very clever.' Yeah. They don't say, 'Stephen Hawking--shit at football.' ") In Britain, however, they are household names, as much as Jerry, George, Elaine, and Kramer are here. If you were alive in England in the nineties, Coogan's character Alan Partridge was one of the cultural icons by which you measured time, a Malvolio of media personalities, on a direct line of wit between Basil Fawlty and David Brent. A hapless talk-show host demoted to radio d.j., Partridge was mean-spirited, self-aggrandizing, status-seeking, forever tempest-tossed in the Sea of Me. He was also a fun-house reflection of Tory Britain, the ultimate Thatcherite Middle Englander. His three series on BBC2 riveted the country from 1994 to 2002, attracting as much as twenty per cent of the audience share and selling more than half a million DVDs.

For a few years now, Coogan has been sowing the seeds of a successful acting career as well. He is the only British comedian since Dudley Moore to make significant inroads into the movie market, with fine performances in such films as Jim Jarmusch's "Coffee and Cigarettes" (2003), Michael Winterbottom's "24-Hour Party People" (2002) and "A Cock and Bull Story" (2005), and Sofia Coppola's "Marie Antoinette" (2006), as well as some not so fine outings in such big-budget Hollywood movies as "Around the World in Eighty Days" (2004) and "Night at the Museum" (2006).

By Coogan's second day on the set of "Curb Your Enthusiasm," according to Mandel, "it was just like he's one of the regulars. It's very simple to see when Larry's having fun." Mandel was holding the day's script--a single piece of paper with seven typed lines--which gave the basics of the plot that Coogan, David, and Hines would flesh out through improvisation over the next eight hours: Larry, in an effort to get himself out of the doghouse with Cheryl, who has moved to a rental in Malibu, takes Dr. Bright there and tries to persuade him to accept the blame for everything that has gone wrong. As the crew positioned the lights around the wicker living-room furniture and adjusted the curtains of the bay window overlooking the glassy Pacific, Coogan, in conservative psychiatrist garb--blue gabardine suit, suede shoes, and glasses--milled around the set in a kind of focussed, anonymous solitude.

Once the actors had blocked out the scene, he and David began to improvise an argument about who should take responsibility for David's marital crisis. "I'm taking ninety per cent of the blame," Coogan said. "I'm asking you to take ten per cent." David refused; mayhem ensued. After each take, the writers huddled around the actors and rearranged the syntax of the scene, clarifying ideas, cutting excesses, adjusting words, resetting props, and debating character points. Gradually, they built up a grammar and a rhythm for the exchange. Around the fifth take, as the argument about Dr. Bright's percentage of responsibility escalated, David began to crack up in the middle of the scene. Two or three times, he started to speak, then collapsed in guffaws. "I'm so sorry," he said more than once. On the sixth take, Coogan's exasperation--"I take one hundred per cent!"--set David wheezing like a tire deflating. He covered his face. "I can't help it," he said. On the seventh take, Coogan nailed it. He spoke of Larry as being under his "auspices"--a pompous term that somehow captured the preposterousness of the man and his situation. "That was pretty wonderful," Mandel said, under his breath, and called, "Cut."

During a break, David noticed me scribbling on my notepad and sashayed over. "Why did I let you on the set?" he asked, then dictated, "Larry David looked pensive before the shot," and headed off with a pensive look on his face. I asked him what was so funny about Coogan. ...