Once upon a time, nobody expected the Spanish Inquisition. Then plonkers began to demand it. In that instant, a phenomenon ceased to be. It joined the choir invisible. It became – you get the idea – an ex-phenomenon, pining for the comedy fjords.

How many times can you tell a joke before it ceases to be funny? Only the ghost of Groucho Marx could supply an answer. For the rest of us, all that survives is a Paramount Comedy Channel rerun of the Spanish Inquisition or the Parrot Sketch and the feeling, like bad lunch returning: enough, already.

It was unthinkable, once upon another time, that Monty Python would cease to amuse. Today, it is doubly unthinkable that I might take in Eric Idle’s Spamalot, if stuck in London. The chances of me reading Michael Palin’s Python diaries are meanwhile slim: I have VAT regulations to digest first.

How did this happen? The Paramount reruns were one clue. Stranded in the wastelands of satellite programming a few months back, the temptations were strong. Python, obviously, said the inner juvenile, given the dismal alternatives. Even if the pleasure was probably nostalgic, the brand came with guarantees. This stuff will always split your sides like a cleaver. Correct?

Not quite. At first I thought the problem was familiarity. I was that juvenile. As the 1960s became the 1970s – October, 1969, to be pedantic – the word-of-mouth began. I think I caught up with it by the third episode. I seem to remember telling myself, nevertheless, that Spike Milligan’s Q5 had been there, done that, and set light to the T-shirt. In those days, the idea that Python was born of stupendous originality was reserved for anyone who had never read Puckoon, or heard The Goon Show. Still …

Still, it was funny. What was there to dislike? They did script cut-ups that William Burroughs had not imagined. They did grotesques that were almost Dickensian. They took Milligan’s contempt for the punchline and followed the strict rule: reductio ad absurdum. In that late-Vietnam period, above all, the absence of a pay-off was the pay-off.

Besides, even if the thing was a touch middle-class, it irritated your elders and baffled your teachers . Never doubt the value of a secret language for 13-year-olds, never despise the value of literacy, and never doubt the efficacy of any light entertainment that failed to involve Ken Dodd or Benny Hill. When I were a lad, ’appens, a handful of hot gravel were better than Benny bloody Hill … Benny and Doddie were more readily available, however.

The Pythons back then were rare, not original. Channel 4 – trust me on this – did not exist in those dark days. Back then, we made our own interactive programme-planners from sticky-backed plastic and egg boxes. We believed in revolutions, too.

I chuckled a bit over the Paramount reruns. Only someone as autistic as a chancellor of the Exchequer could have failed to chuckle when he knew what was coming next. I never managed an entire episode, however. I could not bear the damnable lumberjack, the battlefield re-enactments or the groping of Carol Cleveland. I couldn’t stand the sense of effortless Oxbridge superiority over jokes with the bloated lassitude of Mr Creosote after the last waaffer-thin mint. As I nodded off, the blasphemy fell from my lips: not funny.

Those whom the great British public would destroy, they first turn into institutions. Revolutions – this may be ponderous, and somewhat French – devour their children. Watching TV for money over the years I had a rule of thumb: anything involving a former Python was liable to be “silly”, but dull.

Terry Jones has debauched a true scholar’s knowledge of the Middle Ages repeatedly. Michael Palin’s simpering travelogues can still drive me up the nearest ruin. Eric Idle pulled off a splendid joke about The Beatles (and the Pythons) with The Rutles, then chose assisted creative suicide in California. Finally, there is the authentic test of Python faith. Try it at your next party. “Be honest” – you will say, giving up the ghost – “did you really think Fawlty Towers was even once, even by chance, even remotely funny?”

Such is the legacy. The late Graham Chapman aside, they have each dined well, earned well, and been re-employed repeatedly on the strength of a single show. Worse, their revolution has turned Stalinist: everyone who offers amusement to the public must these days render obeisant gratitude to a bunch of ancient sketches. Why?

I feel a metaphor coming on. Isn’t modern Britain that same recycled joke? Isn’t contemporary British culture merely the art of endless, greedy assimilation, turning yesterday’s revolution into today’s conformity, into spam, into meat and meet? Python has become light entertainment, and it demands its cultural shrubbery. Or as the Americans would say, it has become – let there be – lite. Nothing dangerous, nothing that might be serious. Just a little tyrannical.

Idle’s Spamalot – haven’t seen the show; hate the title – seems to complete the process. They gorge on their own entrails, these old men. They cannot be bothered to work together, without lawyers present, but they keep the brand alive while indulging the fiction that theirs was the finest comedy in a century. You can laugh now, if you like.

Thanks to comically obese Americans, Python has hobbled British comedy for almost four decades. Idle has a musical? All hail. Palin has a memoir? All chortle. In the meanwhile, someone forgot to say that the Ministry of Silly Walks became the Ministry of Silly Wars. A liberal idea has become a conservative force in this culture. Eddie Izzard, though he may not have grasped the fact, has more invention in his girdle than these wizened mentors. Yet Python rolls on.

Grant them this: The Life Of Brian is the idea they should, if hungry and intelligent, have pursued. Each remains fiercely proud of that piece of work. God (and gods) we could do with it now. Yet even today, you sense what they once sensed: here was a trick that couldn’t be missed. Authentic satire, that Oxbridge intelligence brought to bear on the infinite variety of nonsense this world has to offer, the gag in search of a truth: simple. But they couldn’t be bothered, and preferred to bicker.

Instead, these days, they pummel us with that failsafe old joke about ripping off the dickhead punter. Album after album, film after film, book after book: you have to be stupid to buy this latest piece of merchandise, they say. Idle’s musical seems to slot easily into the format. It exchanges respect for irrision. It settles a yoke on the shoulders of British satire, at a time when our satirists are required, somewhat urgently. It also invites deeply unsettling questions. Such as, what is Always Look On The Bright Side Of Life doing in a musical of Holy Grail?

I’ve met a few of them. That would be those self-styled Pythons, your honour. Jones, Palin, Gilliam: I’d recognise those jokes anywhere, if it please the court. They were proceeding along in a routinely entertaining route, m’lud, and came upon a quantity of cash and publicity thereafter. I took notes.

Palin appears to think hard about every question, and appears to care desperately about his answers: you choose. Jones likes Celts, Edinburgh pubs, and Highland malts. Gilliam is perhaps the least-responsible major film-maker I ever teased, but funny, long-winded and visionary with it. He is, self-evidently, the most interesting of them all.

In the olden days they each maintained the party line in those routine interviews. “Python?” they would say. “Tricky. Complicated. Possibly.” At those various times, as now, it struck me that a bunch of plump middle-aged chaps were pushing their luck, and more than somewhat. This wasn’t the Beatles, after all. The Flying Circus contained too much money, too many egos, and too few pressures to excel. Lazy, I thought then.

Laughter in Britain has become precious. Times are hard, governments harder. Python’s 1970s liberation has become a force of reaction, a piece of good old white British middle-class nostalgia preserved at the expense of originality. It is all too comfortable and, yes, too silly. Very. The point was to challenge all, not to entertain theatre coach parties, or edge closer – arise, Sir Mike of Palin – to respectability.

Could it be worse? I’m not laughing. No one expected the endless disquisition. Still, look on the bright side.