Everything changes when you enter the Jillyverse. Everything is warmer somehow, jollier, lovelier, more heavenly. It begins the moment I step out of my taxi at the Chantry, Jilly Cooper’s home of 40 years in Bisley, Gloucestershire. Jilly is there to greet me on the porch: knowing smile, dancing blue eyes, her distinctive white-blonde mane as fluffy as ever, wearing a thick woolen sweater with an embroidered greyhound motif. She’s 86 now and just a tad frail, but she is still a masterful hostess, curious and convivial.

It’s a warm afternoon in the Cotswolds, but the fire in Jilly’s sitting room is roaring. There is a glass of chilled champagne and some smoked salmon blinis waiting for me. And a barrage of compliments. “You’ve got great eyebrows, they’re positively Byronic,” she tells me, somewhat generously. “Umm, thank you,” I stutter. “Oh, I love Byron, wasn’t he heaven?” And we’re off. I’ve been seduced within 90 seconds.

We walk through a home full of dogs: wooden dogs, portraits of dogs, woven dog cushions, dog-eared copies of Dogs Today magazine. There are no live dogs, because “darling Bluebell”, her greyhound, died a couple of years ago. She has been planning to adopt another rescue dog but had to do “15 months” of rewrites on her latest novel, Tackle!, which is what I’m here to discuss.

To be clear, I am absolutely not here to discuss Rivals, the upcoming, star-studded, eight-part Disney+ adaptation of her classic novel, with Aidan Turner (“lovely”) and David Tennant (“heaven”) and Danny Dyer (“they’re all heaven”). In fact there’s a note on the table to remind her that Disney wants her to keep uncharacteristically shtoom. “It’s too early to discuss Rivals, we’re here to discuss Tackle!, but we’re so excited for you to see it etc,” the note says. “Very bossy, aren’t they?” Jilly says, grinning. Still, she assures me, this show is going to be “just heavenly”, much better than the “dreadful, dreadful” 1993 TV movie of Riders in which her swaggering anti-hero Rupert Campbell-Black was played as a “total wimp” by Marcus Gilbert.

“Oh, I love Byron, wasn’t he heaven?”

There’s no Internet in the Jillyverse, no computers or smartphones. She still types out her books on a typewriter called Monica. Except Monica is a little tired now, so Erica the back-up is being an absolute brick and getting the job done in her stead. Even the football chat is different here. Tackle!, Jilly’s 18th novel, features Rupert buying the local football team, Searston Rovers, and bullying them all the way to the Champions League final in his indomitable style. It’s (very) loosely modeled on eco-millionaire Dale Vince’s ownership of her local team, Forest Green Rovers. Except of course Rupert does a far better job. “Forest Green are doing very badly,” Jilly says. “They were the first veggie club [they’re actually full-on vegan]. Then they appointed a woman as manager and she only lasted two weeks. That’s quite anti-women, isn’t it?”

She’s not a Vince fan, it seems. For a long time the former Just Stop Oil benefactor lived in nearby Rodborough Fort. “I think he has moved out,” says Jilly, who stores gossip with the passion of a Victorian butterfly collector.

A key part of Cooper’s appeal is her ability to guide you into a dazzling world you might otherwise never see; to create multiple Jillyverses and fill them with giant egos, volcanic affairs and high-stake but happy-ever-after dramas. She did it first with Riders in 1985 when a savagely seductive Rupert fought his way through the world of international show jumping. She did it with Rupert and Declan O’Hara laying waste to the Tristrams of television in Rivals in 1988, with the moody and mercurial Ricky France-Lynch in Polo in 1991 and again with the tempestuous composer Sir Roberto Rannaldini in Score in 1999.

These have never been great works of literature, but she is diligent in her research and turns a charming phrase. “What was the point of becoming famous anyway?” she once wrote. “The press dumped on you when you were alive, and pigeons when you were dead.”

Cooper still types out her books on a typewriter called Monica.

Now it’s football’s turn. Jilly’s genuine interest was kindled in part by a lunch with Alex Ferguson, in which the purple-nosed Glaswegian despot explained the joys of the beautiful game. “He’s sweet. He’s gorgeous.”

I’m a lifelong Manchester United supporter but I don’t think I’ve ever heard Fergie described as sweet. After all, this is the man who pioneered the half-time “hairdryer treatment” in which he would rage at underperforming players. “I could never understand the hairdryer thing,” Jilly says. “For me it’s something one uses for one’s hair, but he did it to their faces, did he?”

Anyway, Sir Alex was “charming” and “very giggly” at lunch. “I got pissed, I don’t know if he did.” He probably did, but he also lit the fuse of footballing passion inside her. “He said it was the most thrilling and exciting and powerful thing in the world. And it is, isn’t it?”

In recent years Jilly has become a devotee and watches the games on the big screen in her husband Leo’s old office — he died in 2013. Officially she’s a Manchester City fan. “I love [Pep] Guardiola. And Philip Foden. He’s a sweetie, a good boy,” she says, making him sound like an excitable Labrador. She “loves” Harry Kane as well, “but he’s quite stupid, isn’t he?”

Naturally Jilly follows all the gossip too. She was greatly amused by “lovely” Marcus Rashford smashing up his $860,000 Rolls-Royce. She’s worried that the “Tin Hague fellow” (Erik ten Hag) has lost control of the Manchester United dressing room. And she is only half sold on Gareth Southgate, who has given her a signed and framed England shirt, courtesy of her son-in-law, Adam, who works for the League Managers Association. “He’s a sweet man but he’s quite stuffy about his selection,” she says. His real crime, it appears, is not giving her darling “Philip” Foden enough game time.

I missed the 1970s, but entering the Jillyverse feels like a close facsimile. The sexual revolution hasn’t burned out here yet. Masculinity remains an untamed, feral force (one of her footballing stars is called Feral Jackson). There are still pictures of Radley College first XIs from the 1950s in the downstairs lavatory. Mozart is playing on the wireless. And Jilly is still a bit cross about the time George Best stood her up for an interview. “Very wild, wasn’t he?”

In the Jillyverse one can still talk like Prince Philip with the cameras off. “The women are quite different [to the men], aren’t they?” she says of the England Lionesses and their dressing-room dalliances. “It’s riveting.”

In the Jillyverse one can still talk like Prince Philip with the cameras off.

In class terms at least, the world of football is a departure from Jilly’s usual fare of polo, show jumping and art-world philandering. But she wasn’t always quite so patrician. Born Jilly Sallitt in 1937, she grew up in a “rugger family”, the daughter of a brigadier, in Ilkley, West Yorkshire, and then Surrey. She started out as a reporter on the Middlesex Independent, where she covered “everything”, including Brentford FC.

After a couple of years she went into public relations, copywriting and publishing, all of which were a flop. In 1961 she married Leo, a “strong, handsome” Rupert-esque man and publisher whom she’d known since she was a child. On their first date, she once recalled, “Leo unpinned my hair and told me I must never put my hair up again. And then he asked me to marry him.”

The pair lived in Putney, southwest London, and struggled for money until 1969, when a dinner with the Sunday Times Magazine editor Godfrey Smith changed her life. She regaled Smith with her stories of life as a hard-drinking, hard-bonking housewife. He gave her a column, which quickly became her first book, How to Stay Married, featuring sadly forgotten pearls of wisdom such as “your husband must come first” and “if you amuse a man in bed, he’s not likely to bother about the mountain of dust underneath it”.

Jilly and Leo were unable to have children, but they adopted two babies, Felix, now 55, and Emily, 52, both of whom still live nearby and have given her five grandchildren. “I don’t think I was a very good mum, far too busy writing books, but we still love each other very much,” she reflects. Despite all her pearls of marriage wisdom, things were rocky at times with Leo. In 1990 it emerged that he’d had a years-long affair with the publisher Sarah Johnson.

“Adultery hurts very much when it happens to you,” Jilly recalls. “But people just do it.” She pauses for a moment. “I was very lucky, I had 53 years of Leo, he was sweet and funny. And he had to be married to me, which is jolly difficult.”

Johnson told her story to the newspapers, but Leo and Jilly endured. “I forgave him. One did,” she says. “And he couldn’t leave me, he couldn’t afford to, poor boy.” One “wonderful” thing did come out of it, though: “I went down to seven and a half stone.”

Leo Cooper “had to be married to me, which is jolly difficult.”

Although she has to “rewrite everything ten times”, Jilly’s books have flowed at a rate of pretty much one a year since How to Stay Married. She is still planning another novel after Tackle!, which might be set on a posh group holiday to Greece, riffing off ancient Sparta’s positive views on adultery. “It may be rubbish this book,” she says, “but writing is what I do. And now Leo is gone.” She must still miss him. “I do. It sounds silly this, but because he had Parkinson’s, it’s such a shocker. You almost get to the place where you think, ‘Please God, take him.’ Then you feel terribly guilty. It’s not fair.”

Part of Jilly’s magic has always been acute observation of the upper classes, which she has effectively migrated into. Growing up she was “very middle”, but then she met “all these frightfully grand men, so got a bit of practice for Rupert”. Aristocratic decadence has proven an ideal canvas for her bonkbusters. “They are unbelievable the upper classes, aren’t they? They just have to screw. They’ve always been like that. I suppose it has changed a bit today as they don’t want to get whatsitnamed.” (She means #MeToo’d.)

In her glittering but muddy world of gin and gun dogs, Jilly naturally befriended the Parker Bowleses: Camilla and her first husband, Andrew. “The first time I met Camilla I wore a miniskirt and fishnet stockings, very tarty looking. She looked me up and down and said, ‘Oh, Andrew had 35 Valentine’s this year.’ Keep off the grass.”

Today she thinks Camilla is doing “amazingly” as Queen. “She’s looking absolutely gorgeous. She’s adorable. But she is having to work terribly hard. Normally she’s just reading books and riding horses, but now she has to get up and go to three different things. It must be quite exhausting.” She’s slightly less effusive about the King, who is still “settling in” to his role but does “good things for the countryside”.

“They are unbelievable the upper classes, aren’t they? They just have to screw. They’ve always been like that.”

And the two princes? “It’s an awful mess. Why can’t they just put their arms around each other and hug and make up? Of course they [the Prince and Princess of Wales] are livid about the book. She’s very beautiful, Kate, isn’t she?”

We move to the kitchen for lunch — quiche Lorraine and a tricolore salad lovingly prepared by “heavenly” Carol, the housekeeper. Jilly is drinking slowly, but I’m four glasses of champagne down and I must admit the conversation begins to unravel slightly at this point. We cover the sexual proclivities of our previous two prime ministers, Liz Truss (“hysterical”) and Boris Johnson (“he says, ‘Oh Jilly, so nice to see you,’ but his eyes go whoom, whoom, to see over your shoulder”). In fact she’s generally a bit underwhelmed by our former PM. “Boris is writing this Daily Mail column. I think it’s quite boring, don’t you? I think he probably got a bit depressed.”

There is wine at lunch too, so this seems like an appropriate moment to tackle properly the subject that lies at the heart of her entire oeuvre: sex. “I’m quite depressed about sex at the moment,” she says dolefully. “I don’t think people are having nearly so much fun. And everywhere you go, people are marrying their own sex, aren’t they?”

In Tackle! the cat is called Mew-Too. Jilly is concerned that since the #MeToo movement we’ve become too “tense” and “anxious” about sex. “This woke thing is awful. Have you ever been woked? You put a hand on somebody’s shoulder and you’re assaulting them. In the old days if someone was awful to you you’d tell them to eff off and that would be that. Still, I had some horrors in my time.”

Jilly says she has rather given up on sex herself. “I do get propositioned a bit,” she says. “I think people think they might find a rich wife.” Some friends have suggested trying out dating apps, but it’s a no from Jilly. “Can you imagine going on a dating app? I couldn’t think of anything more terrible. You wouldn’t be able to rush off and leave if they were awful. Poor man has come all this way. You’d be stuck, wouldn’t you?”

She’s particularly distressed by the decline of the office affair. “Office romances are wonderful,” she says. “Heaven. Such lovely affairs I had in the office. I loved them. When I was young I was sacked from 22 jobs. I used to look around the places and see how many super-tax husbands were there in the office, and then I used to go and work there. It’s not like that at all now.”

“This woke thing is awful. Have you ever been woked?”

Nowadays even the once incorrigible shagger and general menace Rupert has calmed down, staying faithful to his wife, Taggie, and playing a surprisingly paternal role to his football players in Tackle!. “Rupert’s mellowed terribly,” Jilly says. “He’s so nice now. In the old days he was very cruel to his horses.”

But even as a mellow sixtysomething, Rupert remains Jilly’s platonic ideal of a man: brutal and passionate. She’s rather less taken with the modern vision of masculinity she sees on television. “There’s nothing you really want to sleep with. They’re not nearly as attractive as they used to be, not nearly as macho. I like strong, powerful men.” The problem with modern men is that “they’re always washing up. Not that there’s anything wrong with washing up, it’s lovely, washing up, but you know what I mean? They have to try to be more caring, not masculine. It stops them being so attractive.”

She was baffled, for example, by the response Stanley Tucci received at Wimbledon this summer when they went with his wife, Felicity Blunt, who is also Jilly’s literary agent. “Everybody says, ‘Out the way, I want a selfie with Stanley.’ They adore him. What is that? This is a little bald man who is a sex symbol. Don’t you think that’s a mirror of our age? He’s sort of anti-glamour. Stanley’s adorable but he’s not Rock Hudson.”

This kind of catty tittle-tattle is not incidental to Jilly’s appeal: it really lies at the heart of it. People of all stripes, from myself as an undersexed teenager to the prime minister, Rishi Sunak, who recently told the Today program he is a huge fan, come back to Jilly again and again because it’s all such bloody good fun. She may seem frightfully old-fashioned, but as the world becomes scarier and more judgmental, the appeal of gorging on life with the priapic residents of Rutshire hasn’t dimmed a jot. “The world is deep and dark and full of tigers,” she wrote in Jolly Super, her 1971 collection of nonfiction. “And we need those shimmering white castles in the air to creep into when life gets unbearable.”

Sunak got a thank-you note for praising Jilly, as pretty much everyone does. He has also been invited for lunch, where I imagine he will also be offered bubbly and compliments on his bushy eyebrows. After three splendid hours of my own lunch, I have to be rolled out of the Chantry and into a taxi. Our last conversation is a spirited debate about who was more of a shagger, Bill Clinton or JFK. I mention a threesome anecdote I once heard about the latter. “Ohhh, threesomes, yes, gosh.” Did she ever have one? “I was around in the 1960s, you see. Everybody did everything in those days.”

And on that appropriate note, I exit the Jillyverse for the 15.31 from Stroud to London. A few days later I receive an effusive thank-you card with some hounds in footie kit on it. For just a moment I’m back in Bisley again, where I can still hear the crackle of that jolly fire, taste the champagne, and imagine the flutter of those famous eyelashes. Lovely. Heaven.

Josh Glancy is the Washington bureau chief at The Sunday Times of London