Peter York, co-originator of the Sloane Ranger and a decades-spanning chronicler of the Kensington and Chelsea scene, is in shock. “San Lorenzo? Closing? No! Say it’s not true!” he screams when the bad news is delivered over the phone. “Well, what can I say … a nation mourns.”

Sad but true. The famous Knightsbridge Italian, Osteria San Lorenzo, established in the 1960s and peaking during the Eighties and Nineties — a daily hot fuss of big-hair and shoulder-padded Chanel action — appears to be yet another victim of the pandemic.

Recently, the owners announced that its door will open no more to the push of a Cartier Juste Un Clou-banded wrist and that the very last platter of its famous crudités con bagna cauda (a warm Piedmontese dip with anchovies and walnuts) has been served to SW3’s X-ray figured lunching ladies. The final grissini breadstick has been un-sheathed, the last pap bulb flashed. It is the end of an era and a pasta primavera.

Ronnie Wood and Rod Stewart, on a rainy evening in 1993.

“That era actually being about 20 years back, of course,” says York, rallying now. “San Lorenzo belongs to a time of Nigel Dempster, of Dai Llewellyn, floppy-haired, modelizing playboys, open-neck-shirted Euros and Mayfair Mercenary types in Piero di Monzi jeans and horizontally striped, silver fox furs. All wonderful stuff. I hadn’t been there for years, of course, but I always loved that it was still going.”

Jerry Hall (before Rupert Murdoch).

Indeed. Cash only (no credit cards at San Lorenzo), once at the very cutting edge of cuisine and at the epicenter of London’s fizzy, flash-pulp thrum — its super-glam, tratt-pack habitués numbering, variously, Hugh Grant, Jemima Khan, Guy Ritchie and Gwyneth Paltrow, Boris Becker, Elton John and Sting, Terry O’Neill, Eric Clapton and Mick Jagger, Jack Nicholson, Rod Stewart, Margaret Thatcher, Madonna, Kate Moss, Johnny Depp, Al Pacino and many more — had been looking increasingly out of step with the gastronomic and gossip Zeitgeist in recent years. It had become a tired, old, grilled sea bass kind of girl trying to compete in a revved-up, Sexy Fish environment.

As far back as 1998 AA Gill was predicting its demise, calling San Lorenzo “laughably overpriced” in a scathing Sunday Times review. Still, one visited not for the pasta but for the theater. Stuff happened at San Lorenzo.

The final grissini breadstick has been un-sheathed, the last pap bulb flashed. It is the end of an era and a pasta primavera.

The legendary proprietor Mara Berni — who received each visitor (including me) with the full embrace and double-cheeked kiss of a long-lost relative (Princess Diana called her “Mother Confessor”) — liked to recount the story of the Rolling Stones ringing her bell at 3am demanding that she cook them dinner after a late-night recording session. In the 1980s, while lunching with the journalist Peter McKay, the roué and party boy Dai Llewellyn (so-called Seducer of the Valleys) leapt from his San Lorenzo table with a start and darted out of the front door, only to return a tad flustered an hour later. “What happened?” asked McKay. “I suddenly remembered. I left my secretary tied up in the bath,” explained Llewellyn.

Fellow restaurateur and nightclub proprietor Piers Adam went to San Lorenzo twice a week — “dinner on Thursdays, lunch on Saturdays” — for years. “It was so glamorous: playboys like Robert Hanson and Tim Jefferies holding court on one table, often with the most beautiful models as their dates, and a bona fide superstar like Joan Collins on the next. And I don’t care what anyone says, the food was fantastic — proper first-generation, London-Italian stuff. Delicious.” Adam would have a plate of spicy pomodoro spaghetti schillaci, “several bottles” of white wine and “around half a dozen” limoncello digestifs, mostly on the house. “Mara was the best host. She made you feel like family. When it comes to restaurants, Italians do it better.”

Lorenzo and Mara Berni with family.

Opened by husband-and-wife duo Mara and Lorenzo Berni in 1963 in a prime, villagey position close to Harrods, Harvey Nichols and Hyde Park, the San Lorenzo story really began with Sophia Loren’s first visit. While in town to film Charlie Chaplin’s A Countess from Hong Kong, the Roman superstar booked a long table for herself and her 12 male guests, the story filling newspaper gossip columns the next day and rubber-stamping the restaurant’s status as a celebrity magnet.

Door darkener: Prince Andrew leaving the restaurant.

Peter Sellers and his then-wife Britt Ekland brought Princess Margaret and Lord Snowdon, while Loren’s early patronage encouraged other visiting Italians to make reservations; director Federico Fellini always ordered pasta followed by a muscular T-bone steak, while Michelangelo Antonioni preferred his food to be served in carefully chopped baby portions of carrots and beans. London’s Italian ambassador was another regular. “He had a very beautiful wife and six children,” Berni recalled. “But he also had this lovely mistress, always the full makeup, with those huge false eyelashes girls wore back then. One day I was looking at her and one of the false lashes dropped off into her soup in front of her — so, very quickly, she took off the other one, dropped it into the soup and ate them both.”

There were (and still are in some cases) many other chichi Italian restaurants for aging Porsche drivers and their heavily made-up mistresses in the Knightsbridge locale — Sale e Pepper, Zafferano, the preposterously cheap and much-missed Stockpot chain and the Eurotrash standby Scalini. But only San Lorenzo had Diana.

Joan Collins with grandson Weston in 2007.

During her 1980s and 1990s prime, it sometimes seemed as if every key moment in Princess Diana’s complex love life was playing out against the Gian Codemo gouache artworks on the walls of the so-called “Berni Inn”. Diana lunched at San Lorenzo with her brother Earl Spencer and her young children, Prince William and Prince Harry, but also quite openly with her rumored boyfriends, James Hewitt and James Gilbey. The trattoria’s Beauchamp Place location (you say it “beech-am”, darlings) was a narrow, kettling traffic jam of a Knightsbridge thoroughfare, ensuring that every Diana arrival would engender an interlude of rubbernecking roadblocks, honking car horns and camera flashes.

Elizabeth Hurley and Hugh Grant arrive for a dinner hosted by Valentino Garavani in 1998.

So potent a combination was San Lorenzo and Diana that it even fired up an adjacent business: London’s paparazzi would wait patiently on the barstools of the Maroush, the Lebanese restaurant opposite, Pentaxes primed, chewing on falafel wraps while they waited for the princess to show up. Heady days, but now 25 years ago — the equivalent of a whole century in restaurant years. “But what a lovely little cameo from a long-lost world it was,” says York, now close to tears.

Sans Diana. Senza San Lorenzo. Knightsbridge, and a nation, mourns.

When the crowds move on …

Simon Mills is a U.K.-based writer