Monty Python isn’t dead; it was just resting. Suddenly the seminal comedy troupe seems to be everywhere and, oddly for such quintessentially British humour, it is America shuffling it back on its mortal coil: a show of Python japery is wowing Broadway after televisual repeats acquired cult-viewing status stateside.

Terry Jones, Python founder, reveals that unseen sketches have recently been discovered, including one called the Fat Ignorant Bastard World Convention, and the Python records may be re-released. And how about this for symmetry: 40 years on from when the Oxford Review that metamorphosed into Monty Python made its Edinburgh Festival debut, Terry Jones’s son has a film opening at this year’s cultural thrash.

There is much debate in these insecure times about what defines Britishness: what if, rather than banal citizenship ceremonies, immigrants were made to watch and comment on Python: the cheese shop sketch, the “I ’ad it tough” Yorkshiremen, the Ministry of Silly Walks, the lion tamer — anybody who understood these gags would surely understand what it means to be British. True, some immigrants might conclude that we are decadent and certifiably insane, but it is hard to think of a better way of fitting into Britain than learning to laugh with Python.

We start by talking about that festival of 40 years ago, where Jones met one Eric Idle and the Python we know and love was born. “I remember it very vividly,” says Jones. “It does not feel like 40 years ago; we thought the festival was going bananas because the fringe had 250 shows; now it has 3,000.” In a suitably macabre touch, they performed at the parks and burials department and stayed in a masonic lodge — boys in one dorm, girls in the other.

“We had a rejects night. The Oxford theatre group would put on a play, then at 10.30 we would put on a revue. The Cambridge group came over one night and both groups read out sketches neither had quite finished. We invited the audience to stay on and those sketches people didn’t find funny we threw into a bin.”

What might those scraps be worth now? Jones’s son Will’s Brit flick, The West Wittering Affair, is “very funny and largely improvised”. Cripes, a chip off the old block. “Good God no, we avoided all improvisation like the plague. We all saw ourselves as writers, and we only took to performing because we were fed up with how our lines were being delivered.”

So what’s the film about, Terry? “It is an intriguing love triangle, or rather,” he says hastily, perhaps remembering his own recent marital problems plastered over the tabloids, “it is about love at cross-purposes — a weekend that goes wrong.” Much, alas, like the Jones marriage after our man chose to extol publicly the virtues of more flexible marital arrangements.

Jones, 63, then embarked on a relationship with Anna Soderstrom, a Swedish Python fan more than four decades his junior whom he met at a book signing. Mrs J, a biochemist also known as Alison Telfer, invited him to vacate their south London home. Jones is now said to live with Soderstrom in Highgate, north London. “It has been very difficult for my wife,” he says emotionally. “Unfortunately I am not with my wife any more. My wife gets very upset if anything is written.” He pauses. “It’s awful. I’m sorry, I just don’t feel I can say any more.”

Despite it all, he remains on goodish terms with his two grown-up children. Indeed, as well as finding success as a director (Personal Services, Wind in the Willows, in which he also starred as Toad) and as a documentary-maker, Jones is known to a younger generation as a writer of children’s fiction and one of his books, Erik the Viking, was custom-produced for Will. “I had written at the beginning that he was looking for his father and I forgot about that by the end. Will was most insistent I should complete the story with finding his father.”

Despite the fun of Python, Jones is not nostalgic. “We see each other anyway. We are all good mates. I have just moved to north London and Terry Gilliam is five minutes away and Mike (Palin) is 10 minutes. Unfortunately the other two (John Cleese and Eric Idle) live on the west coast (of America). I will see Eric in a few days.” Graham Chapman, the other Python, died of cancer in 1989 aged 48.

While fans, like disciples of curiously appealing 1970s rock groups that long ago split in a fury of “artistic differences”, yearn for a comeback tour, Jones throws cold water on speculation that with the revival of interest Python, too, will reform: “It is very unlikely. John wanted to in 1988 when we met in Colorado. Eric started setting something up but Mike didn’t want to do it so it fell apart.

“We are better at sitting down together and having lunch now. Everyone is too comfortable. The hungry search for edgy material is gone. You have to be really on your toes and fight for your contribution to be included. Now we would just be, ‘Okay, if you want to cut my bit out, that’s all right’.”

Yet the success of Spamalot, the musical in America, confirms interest is still there. “It’s very exciting. What Eric has managed to do is popularise Python. It never got more than 9m viewers in the days of fewer channels when top comedy shows like Steptoe and Son could get 14m or even 20m viewers. Python was never totally mainstream.”