Very occasionally, even The Times of London gets it spectacularly wrong. “What is John Cleese doing in this lame hotel farce?” demanded the paper’s reviewer after watching the first episode of Fawlty Towers in 1975. The Daily Mirror pronounced: “Long John Short On Jokes.”

The series ran for only 12 half-hour episodes, yet Fawlty Towers has embedded itself in the culture like no other sitcom. In 2000 the British Film Institute named it the best British TV program of all time.

It has even entered the language: “Don’t mention the war”; “He’s from Barcelona”; and “Que?”.

John Lennon longed to be invited to make a guest appearance. “I love Fawlty Towers. I’d like to be in that. [It’s] the greatest show … what a masterpiece, a beautiful thing.” Kate Bush agreed: “I still think Fawlty Towers is the best sitcom ever.”

And now, 47 years after it first aired, Fawlty Towers has become an artifact, a collectors’ item. Last month, an original 98-page script from the show (the Waldorf Salad episode), taken from the set as a souvenir by a BBC cameraman and forgotten in a bedroom drawer, sold at auction for more than $16,800.

One should never unpack a joke, and even the stars of this short-lived sitcom about the world’s worst hotelier professed to be baffled by its achievement of comedic greatness.

Connie Booth (who played the maid Polly and co-wrote the series) was married to Cleese when filming began and had divorced from him by the final episode. She put the show’s popularity down to Basil Fawlty’s explosive rage in a buttoned-down world, as seen when he thrashes his Austin with a tree branch because it refuses to start. Booth, who became a psychotherapist, sees this as “infantile rage and aggression” given rein within “well-mannered English society”.

John Lennon longed to be invited to make a guest appearance.

Fawlty Towers could never be made today. Not because of its dubious language, national stereotyping and other attitudes now deemed unacceptable, but because Tripadvisor would kill its central premise stone dead. No one would ever elect to stay in a hotel this bad.

“I don’t understand why I still find it funny,” Cleese said recently. “I think it’s because of people’s attitude and not actually just verbal jokes.”

Cleese is right: Fawlty Towers still works because it trades on acute embarrassment and simultaneously parodies and celebrates a certain sort of Englishman, rare when the series was made and now all but extinct.

Basil Fawlty is a monster: a cynical, social-climbing misanthrope, at once terrified of and brutally hostile to his wife, an ingrained Little England conservative under assault from the forces of socialism and sexual permissiveness, loathing all foreigners and technology, forced to be polite to people he despises and blisteringly rude to all others. Basil hints at wartime service, boasting a regimental tie and a convenient shrapnel wound. “I killed four men,” he tells strangers. To which Sybil responds: “He was in the catering corps. He used to poison them.”

Like David Brent in The Office, Basil Fawlty evokes rage, a sneaking sympathy and, above all, toe-curling embarrassment; he is appalling, mortifying and profoundly vulnerable. And despite being wholly invented, he is real. Britain once contained many men like this: angry, neurotic, disliking foreigners and distrustful of women, infuriated by newfangled things and progressive ideas, enraged that, having been through a war, others refused to see the world the way they did.

“I don’t understand why I still find it funny,” Cleese said recently.

I had an uncle like that. In restaurants he would loudly opine on the racial background, political orientation, physical appearance and sexual inclinations of everyone around him. “Is that woman pregnant or just jolly fat?” If shushed he would declare, even louder: “Well is she? I’m just asking …”

Like all great fictional creations, Basil Fawlty emerged from life. In May 1970 the cast of Monty Python’s Flying Circus stayed in Gleneagles Hotel in Torquay, while filming in nearby Paignton. This establishment, without en suite bathrooms, TVs or food after 9pm, was run by Donald Sinclair and his formidable wife Beatrice. Sinclair was an irascible and eccentric former naval officer who had been torpedoed three times in the war. He was very brave, stuffy and permanently enraged. If guests asked for hot water to heat a baby’s bottle, a morning wake-up call or a taxi, his immediate response was: “Why?” He did not want the Pythons in his hotel. Cleese later described him as “the most wonderfully rude man I have ever met”.

When the American Terry Gilliam left his knife and fork at an angle on the plate, in the American manner, Sinclair leaned over and rearranged them, muttering: “This is how we do it in England.” He confiscated Eric Idle’s briefcase and placed it behind a wall in the garden, claiming it might contain a bomb. “Why would anyone want to bomb your hotel?” Idle asked. “We’ve had a lot of staff problems lately,” Sinclair replied.

Michael Palin recalled: “That man Sinclair ran it like a high-security prison [and] seemed to view us as a colossal inconvenience. It’s funny now, but it really did seem like the worst hotel in the world. Everything we asked for seemed to be the most unforgivable imposition.”

The other Pythons soon moved into another hotel, one that actually welcomed guests, but Cleese and Booth stayed on for another two weeks, cheerfully gathering material. The resulting sitcom brilliantly lampooned the old-fashioned attitudes of people like Sinclair and Fawlty, men marooned by modernity — which is what makes the modern accusations of political incorrectness made against Fawlty Towers so absurd.

Donald Sinclair died in 1981, having achieved immortality as Basil Fawlty. Even his passing had the hallmark of black comedy. He is said to have succumbed to a heart attack when some workmen, with whom he had inevitably fallen out, crept on to the hotel grounds at night and painted his car and patio furniture gunmetal gray.

Ben Macintyre is a writer at large for The Times of London and the best-selling author of The Spy and the Traitor, A Spy Among Friends, Double Cross, Operation Mincemeat, Agent Zigzag, and Rogue Heroes, among other books