In Britain’s bucolic Cotswolds region, the arrival of summer is typically marked by a migration. Specifically, the return of a rarefied group to grand country houses in counties like Oxfordshire or Gloucestershire, where preparations begin for a season of hosting guests at picnics, luncheons and events like the Chelsea Flower Show, the Royal Ascot horse races and “the tennis” — shorthand for a center court box at Wimbledon.

Owners of those country estates — let’s call them the one percent of the one percent — of course do not handle such preparations themselves. These are relegated to butlers, whose job, like for others associated with the lifestyles of the ultrawealthy, has evolved.

As personal assistants have been rebranded as executive assistants and child care providers as executive nannies, buttling has become a career that involves not only polishing silver and folding napkins but also lifestyle management.

The modern butler — also known as, wait for it, an executive butler — is still in most cases a man. But he is no longer a grandfatherly type in morning trousers that stays in the background, if not out of sight. More likely, he is fresh-faced, wears a lounge suit with a Charvet tie and is by his employers’ side whether they are at home or not.

“They’re like a private maitre d’ now,” said Nicky Haslam, 84, the English interior designer and social fixture. “In the old days the butler was in the house all the time. Now, if the family is on their yacht, the butler goes with them.”

This was not the case as recently as the 1990s, when butlers for the most part reflected the archetype popularized by characters like Hudson, from the TV show “Upstairs, Downstairs”; Carson, from “Downton Abbey”; or Stevens, from Kazuo Ishiguro’s novel “The Remains of the Day.”

Among that ilk was Michael Kenneally, a mischievous Irish butler employed for decades by my cousin, Sir Tatton Sykes, at his country estate, Sledmere, in the county of Yorkshire.

His antics were legendary. If children were visiting, he would sometimes accessorize his formal uniform with a curly-haired wig or glasses with plastic eyeballs on springs. His pièce de résistance was riding through the dining room after dinner on a bicycle with a port tray balanced on the handlebars, a trick that was noted in his obituary in The Telegraph. When he died at 65 in 1999, his funeral drew a crowd of about 300 people, and he was buried alongside members of the family that had employed him for 40 years. On the headstone marking his grave, the epitaph simply read “The Butler.”

The profession’s evolution in recent decades is a signifier of a societal shift in Britain: What rich people want has changed because who rich people are has changed.

That group’s makeup has shifted from being primarily aristocratic families, the type long associated with traditional butlers, to include a new breed of self-made, high-net-worth individuals who have built fortunes in industries like technology and media and who see butlers less as part of the furniture and more as a flashy accessory.

Graeme Currie, 53, exemplifies the modern butler, a role that he said requires “sparkle, darling, sparkle.” He has been employed by some of Britain’s highest-profile families and was the head butler for 10 years at Weston Park, an estate in the county of Staffordshire that is the ancestral home of the Earl of Bradford and can now be booked for private events.

This summer Mr. Currie — who has tawny hair and, often, a light tan — is planning to travel to various destinations in Europe to buttle at vacation houses. In his spare time, he breeds toy poodles, some of which have competed at dog shows like Crufts.

Mr. Currie is the sort of person who can whip up an espresso martini blindfolded and comprehend the precise level of froth someone might prefer for a coconut-milk cappuccino. He developed such skills in part from a career in hospitality that has included jobs on the Queen Elizabeth 2 ocean liner and at ritzy London hotels like the Dorchester and Claridge’s and restaurants like the Ivy.

“The difference between me and an old-fashioned butler is that I’ve had the experience of people paying for dinner and of always being critiqued,” Mr. Currie said.

Seasoned butlers like him can make around 100,000 British pounds a year, or about $125,000. The job’s starting salary is closer to 40,000 pounds, or $50,000.

For butlers with full-time positions, various costs — food, lodging, even fancy uniforms — are subsidized by employers. And those who work in Europe are typically afforded the same mandatory benefits granted to other workers, like a minimum of 20 vacation days. Many develop schedules with their employers that include regular time off on the weekend or midweek to account for other days when they are expected to work long hours.

Mr. Currie was drawn to the profession for a reason that many butlers are: He is passionate about taking care of people.

“One thing I always say is that I’m very good at remembering who people are and what they want,” he said. “You’ve got to have a whole repertoire in your brain because people ask for things they have never asked for before.”

That repertoire can vary wildly depending on a butler’s location, said Niels Deijkers, the managing director of the International Butler Academy in Simpelveld, the Netherlands.

Mr. Deijkers recalled a story he had heard from an executive butler who was with a family on a yacht. “The client pointed toward the coastline and said, ‘Tonight I’d like to have dinner on top of that mountain — please arrange it,’” he said, explaining that the butler contacted a restaurant in the area, which “set up a table for six and flew in everything with a helicopter.” (Mr. Deijkers estimated that the dinner cost “around $300,000.”)

Andrew Gruselle, 53, has encountered similar demands in his time working on Lamu Island, off the coast of Kenya, where he has managed grand beachfront properties with staffs that have included cooks, housekeepers and pool attendants.

In his typical uniform of loose cotton shirt and seersucker Bermuda shorts, Mr. Gruselle has performed a range of duties: serving trays of fresh mango or papaya for breakfast; arranging water-skiing excursions; recommending fabric shops; securing reservations at the Peponi Hotel, a Lamu hot spot; and wrangling six donkeys to stage a makeshift Nativity scene at Christmas.

“When someone comes out here,” he said, “you have to be very careful that they are looked after properly, and that it’s a seamless experience for them.”

Carole Bamford, 78, expects nothing less of the head butler at Daylesford House, her country estate in Gloucestershire, one of several homes she resides at with her husband, Anthony Bamford, the billionaire owner of the British construction company JCB.

Events held at Daylesford House by the couple, known formally as Lord and Lady Bamford, are among the most coveted invitations in the Cotswolds. This spring Lady Bamford, who is the founder of Daylesford Organic, a popular British lifestyle brand, hosted various lunches with themes inspired by plants grown on the estate like snowdrops and tulips.

Leading the preparations for those lunches was, yes, Daylesford House’s head butler, whose résumé reflects those of traditional butlers, in that he has been with the Bamfords for more than 20 years.

“He was with the queen for about eight years before me,” Lady Bamford said.

But his job also involves many duties expected of modern butlers, too.

Lady Bamford recalled a recent lunch where the menu included lamb, purple sprouting broccoli, a cheese board, panna cotta and rhubarb bellinis.

“Who makes the bellinis?’” I asked.

“Well, the butler,” she said.