The conversation was moving along quite nicely, quite civilly, until it turned -- as all conversations with British comedians must -- to the subject of toupees.

A transformation comes over the man at the mere mention of the word. The head flies back, the eyes tear, the long hands fall limply to the floor beside the chair, and the most ghastly, desperate wheezing and sputtering commences. Speech is attempted.

"Whenever anyone asks me to tell them something funny, I'm just going to say 'toupee,' " vows John Cleese, fighting for air. "It's all you need to say, isn't it? Do you say too-pay or toop?"

An answer is offered, initiating another seizure.

"I'm terrible laughing at them, because I've had three transplant operations myself," the gangly Englishman admits, attempting to compose himself. "But the point about hair transplants is that they're terribly good. Takes an hour and a quarter and 10 days later it's all over. And it lasts you for life."

Doesn't it hurt?

"Not at all," the "Monty Python" alumnus says, ruffling the mop. "It's like a heavy dental thing. You have scabs for a week, but that's nothing. You wash it and there you have it. I've got this strange skull-like head, you see, and I need a bit of hair on top of it or else it looks so long and lugubrious it's like a death's head."

Even with its dark brown and gray fringe, it's still a bit death's-headish. The underslung jaw gives the face a slightly clenched expression, as if matters of great importance were being intensely considered (and not quite comprehended). The brow is protuberant and cloudy, and under it the blue eyes have a maniacal glint, like those of an archbishop on a murder spree.

Which brings us to the subject of fish. Fish are another of the three million and one things John Cleese finds convulsively funny. The word "fish" and the swimmy, gilly things themselves. He's written and starred in a movie entitled "A Fish Called Wanda," in which, as you might imagine, fish figure prominently. He's even prone to wearing fish ties, though he discloses that something terrible has happened.

"Someone has stolen my fish ties," the comedian reveals soberly, as if it were a case for Scotland Yard. "I wear bad-taste ties, just to alarm people. It's so funny to wear a nice suit and an awful tie. I think I might even buy a bad toupee. To shock people."

Toupees. Fish ties. These are the things that occupy John Cleese's mind. Silly things. In one Monty Python skit, he was Minister of Silly Walks. (His specialty was a hugely galumphing goose step, followed by a sort of double-clutching stuttering half-crouched skip.) In "Monty Python and the Holy Grail," he heaved hugely demented epithets in a ludicrous French accent at Arthur and his Knights. And, in "Monty Python's the Meaning of Life" he lectured on the particulars of sexual technique, using his wife as a teaching aid.

In Cleese, silliness is redeemed and made transcendent. Bent forward slightly at the waist, Basil Fawlty, the character he played in the series "Fawlty Towers," seemed forever poised on the verge of raging absurdist fits. Cleese and his then-wife Connie Booth, who together wrote the first season of shows for British television in 1975 (they divorced in '78), struck genius when they hit on the basic premise of having their Torquay resort hotel run by a man who hates people.

"Fawlty Towers" was a jolting shot of pure Cleese, and for sheer physical clowning has few equals. Fawningly obsequious to his betters and abusive to everyone else, Fawlty was the archetypal British misanthrope and fool, and the show itself was a study in the hilarity of humiliation. Part of the pleasure of watching Cleese as Basil derives from the sheer spectacle of seeing a man 6-foot-5 fly apart in a frenzy of chaotic delirium. The other part comes simply from seeing a thing done about as well it can be.

Cleese approaches comedy with an artisan's love of craft. It would be hard to find a more conscious, more calculated funnyman than John Cleese, or one whose style reveals the calculations less. "You wouldn't believe the technical detail to which I worked on those shows," says Cleese of "Fawlty Towers." "During the course of a week, I would decide that during someone else's speech, I should look at him three times. And that the first look would be done one way, and the second another, and the third yet another. It was that technical. And you keep doing it until it feels right in your gut."

The key to Cleese is that he is deeply serious about silly things, as only someone who's devoted a large portion of his life to silliness can be. For him, silly is a science, a religion. He's a metaphysician of silly. And while Woody Allen whines that comedy is like sitting at the children's table, Cleese sees it as surpassingly important. "I always say that if comedy is good enough for Shakespeare and Mozart, it's good enough for me."

He argues, though, that there's more substance to his work than one might suspect. "Not very intelligent people always think that drama is more important than comedy," the comic states, giving the left earlobe a tug. "The only thing needed to sit with the grownups is to make jokes about important things. The Pythons were pretty much dedicated to silliness, but our satire had a sort of root subject that made it not wholly frivolous. Some of Python was exquisitely silly and magnificent. Like the fish dance. There's no way you can say this was a comment on the human condition. It was just stupid. But our best stuff, we always used to say, was about something."

Cleese and the other Pythons -- Terry Gilliam, Terry Jones, Graham Chapman, Michael Palin and Eric Idle -- joined together formally in 1969 to create "Monty Python's Flying Circus" for the BBC. Previously, Cleese had taken a degree in science from Clifton College and a law degree at Cambridge and spent two years teaching college English and history. His performing career began at Cambridge when he joined the Footlights Revue as a writer and performer in a show that, in 1963, opened on London's West End and, after a tour of New Zealand, was eventually brought to Broadway. As part of his comedy apprenticeship, Cleese also performed on television and radio, worked as a journalist for the BBC and wrote material for such shows as "The Frost Report" and "At Last the 1948 Show."

He had known Graham Chapman, who became his writing partner through the Python years, at Cambridge. At about the same time, the other future Pythons began to emerge on the British comedy scene. After Cleese saw a show done by Palin, Idle and Jones, with film bits by Gilliam, he suggested that they pool their resources to make some TV, and after the BBC showed interest, the deed was done.

Collectively, the Pythons have collaborated on four film projects. The first, "And Now for Something Completely Different" (1972), was a compilation of the best of the television shows. The team's spoof on Arthurian Grail romances, "Monty Python and the Holy Grail," was released in 1974, followed by "Life of Brian" in 1979 and "The Meaning of Life" in '83. In all likelihood, Cleese says, "The Meaning of Life" will be the Pythons' last group project. Creative differences is the best and briefest description for what stands in the way of another en masse gathering of Pythons, though, Cleese says, periodic mini-reunions are certain.

"I think that you'll see the Python people turning up in trios, like in "Time Bandits," or in pairs, like in Terry Gilliam's "Baron Munchausen" or "Wanda."

"We were a very happy family when we started in '69," says Cleese. "But there were tensions building up. While it worked, though, it worked well, ironically, because we were such a disparate group. We used to write different types of sketches -- Terry Gilliam's animations were quite different from anything anyone else was doing. Eric wrote very intricate verbal stuff. Terry Jones and Michael Palin tended to write more visually. And all these were quite different from the Cleese-Chapman sketches, which tended to be more structured and perhaps more logical, but usually had to do with people bumping into each other rather hard -- people whose interests did not coincide ... abusing each other."

This sort of detailed insight into the hows and whys of being funny isn't unusual for Cleese. Every character and situation is given the intensest scrutiny for comic possibilities. This extends even to his own style, which he analyzes with a dispassionate severity.

"I've got a kind of intensity about me and a focus of attention -- the ability to focus my attention with great intensity," the comic observes. "I think that is why most of my characters are funny. You know Henri Bergson's definition of humor? Social sanction against inflexible behavior. And that kind of single-mindedness is always the basis of inflexibility. Not all of my characters have been like that, because I play vague characters quite funnily too. But I think that's what people think of me for -- veins standing out in the forehead, that kind of thing."

It was at the age of 9 or 10 when Cleese first thought he might be funny. His father was an insurance salesman and his mother a pianist. Neither was particularly funny. But then again, neither of them had grown to six feet by the age of 12. "I was an only child," Cleese remembers, "extraordinarily tall, thin, slightly solitary creature, and not a very good mixer. Then I discovered than I could make remarks -- slightly cheeky remarks -- that could make the rest of the class laugh. After that, they could accept me."

Though the Englishman is introspective (almost to a fault), this is about as close to personal as the conversation ever gets. A student of psychiatry, and coauthor -- with his doctor, Robin Skynner -- of the humorous psychology textbook "Families and How to Survive Them," Cleese prefers to concentrate on technique. (After all, his first love was science.) And typically, he deemphasizes any innate sense of humor, claiming that it's mostly careful planning and arduous rehearsal that get the laughs. The question this raises is whether to be a comedian, one has to be a student of comedy.

"It depends," comes the answer. "There are definitely people who are enormously funny who don't know why. There was a great English music hall comedian named Tommy Cooper, who is unfortunately dead, who reduced me to a heap in the way almost no else ever has. And a friend of mine who wrote for him said that Tommy never knew why he was funny, and sometimes would go and ask people, quite earnestly, to explain it to him.

"I'm the other end of the extreme," he continues. "I'm the opposite of an improvising comedian, which isn't to say that I don't have moments where an idea comes over me. But I don't even want to improvise. It doesn't strike me as interesting. The great thing about improvising is that it's a trick, like juggling, and it has nothing to do with content. What you applaud in the improvising comic is the speed of the associations, not the quality of the material."

At this point Cleese begins to think aloud about the people who've influenced him and made him laugh: Benny. Burns. Phil Silvers, "whom I rated higher than Benny." Keaton, Harold Lloyd, Chaplin. He claims to have come to Laurel and Hardy late in life, and the same with W.C. Fields, "which was perhaps the happiest moment of all."

He admires Steve Martin -- "great technique" -- and claims to have run a particular bit in "Dead Men Don't Wear Plaid" over and over again in his tape machine, in slow motion, to get the movements down right. Then comes the Englishmen -- Peter Sellers, Spike Milligan, the Goon Show, Peter Cook and the great Tony Hancock.

"I've always said that I had a very catholic sense of humor," Cleese says. "I can laugh at something that is quite dry and misanthropic, like Mencken or Ambrose Bierce, and at the same time adore a knockabout routine."

Rising up out of Cleese at the moment is an awesome memory -- awesome in that it provokes another of the comedian's apoplectic, oceanic laughs. What he's remembering is "the funniest thing I've ever seen!" And oddly enough, he says, he found from talking over tea with the late French comedian and filmmaker Jacques Tati that their "funniest things" were the same. "We were talking, and he asked me the question and I said, 'Jerry Ford arriving at Orly airport.' In front of 800 of the most elite French troops, the entire diplomatic corps and, of course, President Pompidou, Ford steps out of the plane, waves to the crowd and goes tumbling down the stairs."

A tissue is offered and declined and the story continues. "What I didn't know, and what Tati told me, was that he got up, laughed, brushed off his clothes, strode forward with a big smile, and took very firmly the arm of the man standing next to Pompidou -- who was the Spanish ambassador -- and carried him off down the red carpet, leaving Pompidou staring after him in amazement."

Another pause.

"Now this is paralyzingly funny and you can never top it, because it is real!"

Wrapping up this master's class in comedy, Cleese admits that performing is actually something of a bore to him -- that because he could easily visualize what needed to be done "it was like completing a circle, two-thirds of which has already been drawn. I was operating with parameters that were very, very tight, with the basic thought in mind that I had better not foul it up."

So where, the comic is asked, is the pleasure in it? "It's in that moment," he says, "when you're flying, but at the same time not going into self-indulgence. In those moments, you get that little extra joy from knowing you've been genuinely funny."