His customers have included Kate Moss and at least three James Bonds — Roger Moore, Pierce Brosnan and Daniel Craig. His cocktails have entered Parisian folklore. His inventions have influenced bars across the city.

Now Colin Field, 62, is leaving the Hemingway Bar at Paris’s Ritz Hotel after a stint of almost 30 years that has made him a star among the great and good and, by consensus, one of the world’s finest bartenders.

“I love the Ritz but I had become bored there,” Field, who was born in Rugby, said. “I wanted to do more creative stuff, although I don’t mean putting 65 different ingredients into a cocktail. I don’t like the fashion for having so many ingredients that customers don’t know what’s in it and have to wait 15 minutes for it to arrive.” Field says the best cocktails are made with “two or three max”.

The Hemingway Bar had been closed for 12 years when he went to work there on August 25, 1994. It was the 50th anniversary of the liberation of Paris, when Ernest Hemingway, then a war correspondent, had grabbed a machine gun and persuaded some French Resistance fighters to accompany him on a mission to chase the Nazis out of the Ritz, his favorite pre-war watering hole.

The bar, then known as Le Petit Bar, was closed in the 1970s, despite having been visited by luminaries such as Marlene Dietrich, Ingrid Bergman, President Kennedy, Henry Ford, Noël Coward, Graham Greene and Truman Capote. Mohamed Al Fayed made an attempt to relaunch it as the Hemingway Bar after buying the Ritz in 1979, but this proved a failure and it was shut again and used as a storeroom until Field’s arrival.

Under his guidance, the small bar — it has seating for only 25 people in leather armchairs — has become one of Paris’s most exclusive locations, attracting the wealthy and the famous but also a host of journalists along with impoverished, aspiring writers.

“I love the Ritz but I had become bored there.”

Field says he worked on his own there at first, opening the bar at 6.30pm and getting home at 5am. He largely decorated it himself, and introduced what were then novelties, such as freezing cocktail glasses — a practice then unknown in Paris but now widespread.

He was also the first bartender to start the now customary practice of macerating cucumbers in water. He says he did so because his regulars liked to have telephone conversations from the bar — it being viewed as “very chic in the days before mobile phones” to receive a call in the Hemingway. The downside was that this delayed his preparation of cocktails. He would serve water with cucumbers as customers waited, having discovered that they have “the marvelous effect of keeping us calm … and more receptive”.

Some of his cocktails are hailed by connoisseurs as works of genius, such as the Clean Dirty Martini with its olive juice ice cube, or the Serendipity with Calvados, mint, apple juice and champagne.

There is no music in the Hemingway Bar, Field preferring to encourage conversations between customers or often with himself. “They say bartenders have to listen to their customers’ problems, but at the Hemingway, it was the customers who listened to mine,” he said.

Many have become his friends, like Moss, who helped him with the décor by supplying a typewriter in lieu of payment for a cocktail, which he had refused from her. He named a cocktail in her honor, the Kate 76 — a twist on the “French 75” consisting of vodka, sugar, grapefruit juice and champagne — and was bartender at her wedding in 2011.

He says Craig is a “marvelous chap” too, and Brosnan a “marvelous gentleman”. They are his favorite James Bonds, he adds — by which he means those with whom he got on best at the Hemingway.

This month, Anne-Sophie Prestail, Field’s deputy — a “brilliant and creative” bartender, according to the Ritz — was put in charge of the bar. Field, for his part, will continue to work part-time at the Maison Proust, a chic hotel in Paris, but also at special events, possibly including the VIP area of Formula One.

He also plans to open an upmarket guest house in the countryside outside Paris where there are “no neighbors … so you can dive naked into the swimming pool and play the music as loud as you like”.

Adam Sage is the Paris correspondent for The Times of London. He has covered five presidential elections and countless scandals