Imagine a day in the life of a London socialite. She’ll pop into Topshop and pick out a miniskirt; head over to Le Caprice for lunch. She might enjoy a spot of tennis at the Bath & Racquets Club. She’ll definitely meet a friend for a drink at Soho House, where they sill gossip about Kate Moss’s new collection and what fun Naomi Campbell’s fashion show was. She might even reveal who she spotted having lunch in Scott’s the other day - and why she’s really taking her hot new asset manager to George tomorrow. She’ll finish it all off in a box at the theatre, with dinner at J Sheekey’s afterwards.

She thinks she’s being eclectic, but in fact her entire life belongs to two of London’s most colourful gazillionaires. The Topshop tycoon Philip Green owns her clothes - or at least the trendy ones - while his best friend, the rag-trader-turned-restaurateur Richard Caring, owns the hangouts: the jet-set, media and hedge-fund favourites The Ivy, Le Caprice, J Sheekey, Scott’s, Annabel’s.

Of the two, it is Caring, dubbed “the Lex Luther of Mayfair” for his supermarket-sweep approach to buying companies, who is currently attracting the most attention. An enigmatic 59-year-old, he is poised to snap up the Soho House group, an acquisition that would transform him from just another big shot into the most talked-about businessman in fashionable London. And if he goes on buying up the other high-end concerns he is allegedly interested in - including Ben Elliot’s concierge company Quintessentially and the US embassy in Grosvenor Square, which some say he’ll turn into a sexier version of Claridge’s - it is only a matter of time before he has society eating out of his hand.

“He’s setting up the restaurant equivalent of LVMH,” says AA Gill, referring to the French fashion leviathan that owns Louis Vuitton, Celine, Marc Jacobs and Fendi. “He’s spending a lot more on these businesses than they’re probably worth, but eventually he’ll have a portfolio that, as a brand, is worth far more than the sum of its parts.” As Caring himself puts it: “I’m interested in brands where the product doesn’t meet the expectation.” In other words, companies that are worth more in the minds of the consumer than they are in reality, places you go to see and be seen, rather than simply to eat or drink. You’ll go to Le Caprice, for instance, not for the warm duck salad, but for the chance you may be seated next to the Duchess of Cornwall.

And yet, why is he bothering with these overinflated brands? It’s not because he needs the money - he has plenty already (£450m, to be precise). Is it just for fun? Because he can’t resist a new project? Or is it, as the snobbier members of Annabel’s might conjecture, because he’s socially ambitious?

“It’s a mixture of all three,” says a socialite who knows him well but would prefer to remain anonymous. “What does a tycoon do when he reaches 60? He’s worked hard all his life, but now fancies a bit of fun. It’s like active retirement. So he’s out and about more, buying up swish companies. Of course, he loves the social aspect - it’s not a coincidence that this is the territory he has chosen. He loves swanning around his restaurants, sitting next to Madonna at Mark’s Club, or entertaining Liz Hurley at Annabel’s. He relishes being a social puppeteer, and since Green’s profile has soared thanks to working with Kate Moss, part of Caring probably wants to be up there, too. But, fun though it may seem, he’s certainly in it to win it.”

A man with a penchant for posh blondes - his wife, Jackie, is a major’s daughter - Caring clearly finds the social side of things irresistible. “Wealth is something I’ve worked very hard for, and I think you should utilise it,” is his take. Quite.

Last year, he made a flamboyant debut by splashing out £9m on a charity fundraiser in St Petersburg. It was staged at the Catherine Palace over two days; tickets cost £5,000, the guest of honour was Bill Clinton and other attendees included Tamara Mellon, Sting and Trudie and Elton John. News of the bash ignited everyone’s interest. Suddenly, he was everywhere, “a man whose appetite for new best friends is greater than a pig’s for truffles”, it was said. Tellingly, some of the guests were still a little vague as to who their exciting new host was - when some of them encountered him in the lift with a tape measure around his neck, they thought he was a tailor who had come to make alterations to their costumes.

They can hardly ignore him now. Like the love child of the 1990s restaurateur Mogens Tholstrup and Donald Trump, one moment he’s dining with Claire Sweeney, Christopher Biggins and Cilla Black, and the next he’s hanging out in Prince William’s favourite boîte, Boujis. Almost overnight, he has become much more than Philip Green’s trusted sidekick. However, his recent fetish for blue-chip companies - after a lifetime of working with Green in the production of cheap clothes in the Far East - ostensibly stems from an obsession with golf. He bought Britain’s smartest golf club, Wentworth, a few years ago as an amusing addition to his brimming portfolio of tycoon’s toys. It started as a vanity project: “a dream”, he said. “I don’t think anybody would say it’s a magnificent investment, but it does cover costs.” But when he brought Caprice Holdings in to do the catering, his appetite for the upper-crust lifestyle was whetted. In addition to his lavish house in Hampstead (known as “the Versailles of the north”), his collection of impressionist paintings and Louis XV furniture, an aircraft and a boat, Caring has also just got into shooting, with a brand-new lodge in Devon, its interior designed by Tara Bernerd, the daughter of his old friend the property magnate Elliott Bernerd. When asked if he was any good at shooting, Caring replied: “Well, I’m quite good. I can stand in line.”

Rarely out of Armani, he cuts a dashing figure, with his immaculate manners, deep tan and bird-of-paradise hair. Unlike Lex Luther, though, he is universally liked: associates enthuse about his relaxed style and unstarriness. “He’s one of the few businessmen it’s difficult to say anything bad about,” says the Camden gallery-owner Alex Proud. “Old school, well mannered, polite and charming. He clearly enjoys the entertainment side of the business - it’s more fun than running an insurance company.” Of course, there are dissenters - a few old buffers tut-tutted when the chef at Mark’s Club walked out a couple of months ago - but there is no sign that anything is going to his head yet.

Rather, Caring is one of a number of dynamic businessmen, such as Uma Thurman’s boyfriend Arki Busson and Stuart Rose, the CEO of Marks & Spencer, who slip effortlessly between the social and financial worlds. As he puts it: “I don’t feel guilty about being rich at all. It’s not as if I’ve inherited it.” First class all the way, then? “Yeah. What the hell. If I’ve got the choice, I’ve got the choice.”