There comes a time in the life of famous men when they peer over their shoulder and find their son towering over them, physically, figuratively, or both. This is happening to Terry Gilliam, 67-year-old veteran of Monty Python. He is dealing with it manfully, with a little help from Harry, the 20-year-old, 6ft 4in, handsome-as-hell son in question. To hear them talk of how they cope with each other at this sensitive time is like watching a cartoon on the evolution of fatherhood over the past half century.

Harry is two years into a part-time modelling career, having been stopped in the street by a professional hunter called Jane Duval. “A female kerb-crawler,” says his father. He worked for a small agency called Union Models and did a Levi’s jeans campaign. Now he is with Select, which once turned him down because of his unfashionably long hair. He had grown it because his father had cut his. Terry, of course, had often looked like a hippy, but this was a front behind which lived a driven, swotty man. It was good being surrounded by so many genuine hippies, he says; they just floated about and offered no serious competition to the ambitious students.

Forty years on, Harry’s modelling is a sort of front, too, because that’s not his vocation. He wants to be a – wait for it – artist and perhaps film-maker. This autumn he enrolled at the Sir John Cass School of Art in East London. Neither of them wants him to surf his way to success on the famous name although, as both agree, neither can really not be the people they are. It is, as they say back in California, the state of Terry’s own student days, an upmarket problem, but a problem nonetheless. Even when Harry has tried, in the nicest and best-brought-up way, to disown his father, the genetic imperative marches into the frame like a Monty Python boot. Once, when he was studying art, he made an angel sculpture and some fellow students who didn’t know whose son he was said, “Hey, that looks just like the one in Brazil [the 1985 Terry Gilliam film].” “And I thought,” says Harry, “‘Oh no, I can’t even put some things together from a skip without everyone seeing the influence.’”

The question is: whatever happened to Oedipus? Surely there has to be confrontation, even a kind of murder, before the adult son can be himself in relation to his father. Listening to the Gilliams you can’t help feeling that they’re trying to hold talks with Oedipus, broker a peace deal with this implacable warlord. If so, they’re hardly the only ones. One of the defining images in the self-appraisal of Terry Gilliam’s generation is that they just don’t do parenthood like their own parents did; there is a new settlement, brought in by the affluence and enlightenment of those postwar decades; authority has softened into something advisory, fatherhood contains friendship, upbringing entails the consent of the technically junior partner. “Oh, Oedipus never went away,” says Terry. “It pretended to go away. People did think that if you were a different kind of parent you could avoid it.”

So isn’t there this danger of having him (Oedipus) return in his own time for a proper reckoning? Aren’t the Gilliams setting up home on the lip of this volcano? “I’m always aware of it,” says the father. “My attitude is that the king must die and the prince must kill the king.”

“Except that I’ve chosen not to be the prince,” says his son, “but the joker instead.” This sounds just as ominous in its own way. Besides, Gilliam senior has no intention of getting himself killed, either physically or figuratively. That’s the other big change from the generation before Terry’s. Nowadays, parents never die, and the issues hang around until deep into the children’s middle age. Ask these two what they would like to be doing in ten years’ time and Harry says, “Drawing away in some Tokyo studio and getting paid to show my art in a gallery,” while his father says, “Same old s***.” On present evidence, he will be as good as his word, with yet another trouble-fraught movie, The Imaginarium of Dr Parnassus, due for release in this country next year, posthumously starring the Gilliams’ much missed friend, Heath Ledger.

It’s names that give the generation games away. It always has been. Terry’s own middle one is Vance, which was his mother’s maiden name. As Harry says, “All Dad’s friends have their parents’ names in the middle of their own.” There was no way the baby-boomers were going to dump such family rubble on their own babies. Frank Zappa called his daughter Moon Unit and David Bowie called his son Zowie, and he in turn has renamed himself Duncan Jones. The Gilliams came up with Thunder for Harry’s middle name, Rainbow and Dubois respectively for his much older sisters, Amy and Holly. Was that Dubois as in Blanche, the heroine of the classic Tennessee Williams play, A Streetcar Named Desire? Nothing as cultural as that; Dubois as in wood, as in Holly-wood. “Horrible, isn’t it? She was due on the night we were doing Python at the Hollywood Bowl. My wife [costume designer Maggie Weston] kept her knees together for a week, and Holly was born when I got back.”

It’s just possible Harry got his rebellion in early. Very early, about 10. In those days, his father’s look was seedy flamboyance, all loose clothes and flowery shirts. Harry, meanwhile, was beyond preppy, with a dapper blazer and attaché case.

“I don’t know if you were doing that consciously,” his father now asks.

“No,” Harry replies, “it was just because

I wanted the attention to be on me. I thought, I’m going to be different so that everyone looks at me.”

The five of them lived in a bohemian version of luxury in a huge house in the North London district of Highgate, and Harry went to the nearby public school of the same name. There were richer kids there, with even more famous fathers. When they clocked where Harry came from, they did take the mickey briefly by going round after him making clippety-clop coconut noises, as in The Holy Grail.

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