HOW DELICIOUS TO settle in for a cocktail while afternoon tea is being served next door. It’s 4 o’clock on a Friday in early April and I’m at the Donovan Bar, part of Brown’s Hotel, in the heart of London’s Mayfair. It feels risqué. Others are enjoying cucumber sandwiches and cups of Earl Grey tea in the hotel’s Drawing Room, and here I am, sipping a tropical tipple inspired by “The Jungle Book,” penned by the author Rudyard Kipling in a suite upstairs. Fittingly, I’m in the Naughty Corner, an intimate nook lined with racing green banquettes and racy black-and-white photographs by the celebrated cameraman Terence Donovan, from whom the bar gets its name.

Brown’s is a hotel with a storied history. Since opening in 1837, it has welcomed royalty, starlets, world leaders, and literati. The first London telephone call was made here in 1876, and it’s where the brains behind the British Academy of Film and Television Arts first met in 1947. That same year the hotel opened a cocktail bar. Winston Churchill was a regular, and A.A. Milne, too. The bar’s current menu, “Once Upon a Time,” pays tribute to such memorable guests and moments. My favorite offering: The Honey Bear, combining Campari, rhubarb cordial, Sassy Cidre Brut, and a swirl of sweet honey, served in a round glass reminiscent of Winnie the Pooh’s belly.

“It’s about paying homage to the people who make Brown’s what Brown’s is now,” says Federico Pavan, the suited and booted director of mixology, who mans the cocktail menu together with the legendary Salvatore “The Maestro” Calabrese — notably the holder of the Guinness World Record for creating the world's most expensive cocktail, Salvatore’s Legacy, created for the Donovan Bar. This over $6,500 libation unites 1788 Clos de Griffier Vieux cognac, 1770 Kummel liqueur, 1860 orange liqueur, and 1930 Angostura bitters — just a few bottles from the bar’s world-renowned, well-displayed rare spirits collection.

After a yearlong redesign, the Donovan Bar reopened in 2018 with this talented twosome at the helm. The dimly lit space centers on a glass-topped bar that glows an icy blue; the tables are polished metal, the chairs plush velvet. Donovan’s portraits of Swinging Sixties London deck the walls, painted a sleek shade of gray. Though we’re a stone’s throw from busy Piccadilly Circus, this drinking den is a respite — cozy and elegant.

“Of course, the design is picturesque, but it’s the people who make this place special,” says Pavan. The Maestro and his delectable surprises. Fabio Spinetti, the bar manager who likes to mix old and new. The clientele: discerning drinkers, young and old. “When they come here, they feel at home.”

Eager for another cocktail, I flick through the menu, bound in green leather. The theme changes once a year, though the signatures remain, among them Calabrese’s famous Spicy Fifty: a sweet-and-sour combination of Stoli vanilla vodka, elderflower cordial, lime juice, honey, and fresh chili pepper. If you’re feeling flush, there’s a list made with vintage spirits. The sharing plates are hard to resist; I plump for the Involtini, little bundles of roasted red pepper, goat’s curd, and olive — and there are also toothsome mains if you fancy something more filling.

By the time I’m ready to leave, the bar is buzzing. “California Dreamin’” sounds from the speakers. I’m curious to hear how Pavan came to work with cocktails, and he tells me it was an accident. When he was younger, he dreamed of being a Formula One driver, but he broke his shoulder. “I was dating a girl who worked in a bar, and one day she asked me to cover a shift,” he tells me. He agreed, and nearly 15 years later, here we are. I ask what racing cars and mixing cocktails have in common, and he smiles: “Adrenaline.”