Federico Marchetti, a fashion entrepreneur, was a confidant of Giorgio Armani, but he’s stumped by whether it’s O.K. to wear a kilt around the King.

Federico Marchetti, the Italian fashion entrepreneur, is a master of sprezzatura—the courtier’s art of cloaking ambition and cunning in an air of guileless nonchalance. In the early days of e-commerce, he convinced Giorgio Armani, the king of Italian fashion, that selling clothes online would not damage his brand. He also built digital stores for other élite fashion houses, and created Yoox, a high-end online retailer. In 2018, Marchetti, then forty-nine, sold the company at a valuation of six billion dollars. But, instead of retiring, he sought out a new liege. He had served the king of fashion so ably (Armani does very good business online) that it was not entirely surprising when he joined forces with an actual king: Charles III of England.

Marchetti was in town during Fashion Week to promote his memoir, “The Geek of Chic.” (The title is borrowed from a 2012 New Yorker profile of him.) On a Wednesday evening, Silas Chou, a Hong Kong-based textile and fashion tycoon, hosted a book party in his eighty-second-floor apartment on West Fifty-seventh Street. Guests observed a moment of silence for Armani, who had died a few days earlier, at the age of ninety-one, before tucking into what Chou described, not inaccurately, as “the best Chinese food you’ve ever eaten.”

Two days later, Marchetti, who lives in Milan and on Lake Como, was having breakfast at a downtown café outside the Police Building, where he keeps an apartment, talking about his relationship with King Charles. When they met for the first time, in 2017, at an event in London, Charles was still a prince. They bonded over their shoes. “I said, ‘Your shoes look amazing!’ And he said, ‘They’re twenty years old!’ ” Marchetti recalled. “They were perfect, absolutely perfect. And my shoes were perfect, too, and ten years old.” Charles has long been devoted to promoting sustainability in the fashion industry, part of his broader environmental advocacy. “He is someone who is wearing for twenty years the same coat—the camel,” Marchetti noted. He recited a motto of the King’s: “Buy less but buy better.”

In 2021, Charles, admiring Marchetti’s get-up-and-go, invited him to chair his fashion task force. “He calls me his Italian secret weapon, because he loves that I’m an action man,” Marchetti said. Soon, Marchetti was invited to a small dinner at Dumfries House, an estate in Scotland owned by the King’s Foundation, Charles’s charitable nonprofit. (Marchetti is now a trustee.) “The dress code said ‘smoking jacket,’ ” he recalled. “In Italy, we don’t have ‘smoking jacket.’ I had to Google it.” (It refers to a velvet or silk dinner jacket worn with tuxedo trousers.) Charles himself, Marchetti remembered, had on “an amazing outfit with matching colors that only a very sophisticated man can put together. I thought, Oh, my God, you’re so stylish.”

Marchetti felt compelled to acquire a kilt for his new duties; he had one made by a Scotsman, who dreamed up a new tartan, in cream, orange, and gray. (The kilt-maker said that the pattern was “inspired by two national symbols of Italy, the wolf and the lily.”) The etiquette of kilt-wearing, however, flummoxed the Italian. “I was told that, if the King’s not wearing the kilt, no one else can,” he said. (That turned out to be wrong.) Marchetti had also heard idle gossip to the effect that “an international person cannot wear the kilt.” (Also untrue.) So far, he has played it safe, in trousers.

On another occasion at Dumfries, Marchetti made a bold choice because, he said, “I’m a courageous man.” He wore green shoes, a cheeky take on the John Lobb wing tip, made in collaboration with Paul Smith. The gambit paid off with the King and his court. “Now every time they introduce me to somebody, they say, ‘This is the most stylish man of Italy,’ ” Marchetti recalled. (He has persuaded his friend, the movie director Luca Guadagnino, to design the interiors of the Milan and Lake Como residences, which he shares with his wife, the British fashion journalist Kerry Olsen, and their fourteen-year-old daughter, Maggie.)

Marchetti was one of only a few Italians invited to Charles’s coronation ceremony, in 2023; others included the President of the Republic and Andrea Bocelli. For the occasion, his friend Brunello Cucinelli made him a morning suit: white tie, striped pants, and tails. One of Marchetti’s gifts to the King was even bolder than his green shoes: a chrome-plated toothpaste squeezer from Lorenzi, a venerable knife shop in Milan. It was a reference to a minor scandal from years ago, caused by a report, in the Guardian, that the prince’s toothpaste was squeezed onto his brush by a servant.

“His valet told me, ‘You’re a brave man, to bring him a gift like this,’ ” Marchetti recalled. Charles, in a thank-you note, indicated that he was amused.

Does he use the toothpaste squeezer?

“I never asked,” Marchetti said. Even an action man knows that, when dealing with kings, discretion is the better part of valor. ♦