“I owe my career as much to the photos I haven’t published as the ones I have,” says Mr Greg Williams, sitting on the porch of his recently renovated barn-house near Newbury, England. It’s a bright, breezy day in May, and down in the garden, the first signs of summer are beginning to show. Last year, Mr Williams installed his own private fishing lake fringed with what might be Berkshire’s only white-sand beach, the sand imported by the truckload. Today, the lake’s shallows are black with tadpoles, while freshwater trout linger in the depths. At the edge of the shore stands a little wooden hut decorated with a Jolly Roger flag and a lifebuoy from the Hôtel du Cap-Eden-Roc in Antibes.

Fresh from his daily 1km swim, Mr Williams is glad to be home. He has just returned from a two-week assignment at the Cannes Film Festival, where his subjects included some of the most famous people in the world: Messrs Benedict Cumberbatch, Adam Driver and Miles Teller, and Mses Léa Seydoux, Julianne Moore and Tilda Swinton, to name just a few. Many of the resulting photographs were taken on behalf of brands such as Chopard, which has a long-standing partnership with the festival. But many were “self-commissions”, as Mr Williams puts it, destined only for his Instagram account, or for the social media platform Vero, where he publishes a series of “photo breakdowns” explaining how he captured some of his favourite shots.

These personal photographs – candid black-and-white portraits captured on hotel balconies or in the back of limousines – underscore the reputation Mr Williams enjoys among the Hollywood A-list. He’s liked, but more than that: he’s trusted. This much is clear from the unguarded intimacy that seeps through each image, not to mention the unusual level of access he is given. “I try to create a relaxed atmosphere,” he says. It’s because of this ability to put celebrities at ease that he’s become their go-to guy when photos need taking, as they often do if you’re a movie star. “It’s a necessary part of an actor’s job,” he says. “So, I try to make the process as painless as possible. It’s just me, my Leica camera, and the available light. No crew. And I’m in and out of the room in 90 seconds.”

More than speed, what Mr Williams offers is protection. “In everything I do, my first responsibility is always to the talent,” he says. Because of his subjects’ immense fame – he recently photographed Mr Lionel Messi, who has 123 million followers on Instagram – he often finds himself acting as their first line of defence against brands looking to leverage their influence for exposure. “I’m in a unique position, working with the people I do,” he admits. “I get a lot of people approaching me saying, ‘Would you talk to so-and-so?’ And I have to say, ‘They’re not going to like that.’ They won’t appreciate being asked. If I bring things into their lives that they resent, the trust I have with them disappears.” This extends to the photographs he publishes, too, which are all subject to client approval. He remembers his early days as a photojournalist for magazines, filing assignments for The Sunday Times Magazine or Time: “My editors would say, ‘Make sure you don’t give the talent the chance to sign off on the final images.’ It always puzzled me. Why would I want to publish something they’re going to hate? Who, exactly, does that serve?”

He sees his photography as a form of collaboration, anyway, so it’s only appropriate that his collaborators should have some kind of say on the results. And he uses a similar argument to justify working in the celebrity world – one that many see as epitomising glamour over substance. “When I quit photojournalism and started working in the film industry, a lot of my friends would tell me I was obsessed with celebrity and that I’d sold out. They were right, I suppose,” he says with a wry smile. “I had sold out.” He’s unapologetic about it, though. “These are extraordinary people with an extraordinary view of the world. Johnny Depp, Thom Yorke, Gary Oldman… they’re creative powerhouses. It’s an amazing privilege to collaborate with them.” These collaborations often extend beyond the photographic studio, too. Last year, after photographing Mr Mike Tyson, he became an equity shareholder in Tyson Ranch, the ex-heavyweight champion’s cannabis company, which is currently building a 400-acre, weed-themed resort in the Californian desert. “I take CBD every day,” says Mr Williams. “I’m a real believer. I feel the happiest and most content I’ve been in years, although,” he swivels his head, acknowledging his surroundings, “there are a lot of other reasons for that.”

Mr Williams, it emerges, is something of a serial entrepreneur. The styling product used in his hair for this photoshoot is from Saunders & Long, a men’s grooming brand that he launched recently with two old friends (the eponymous Messrs Nick Saunders and Jonathan Long) and the German model-slash-influencer Mr Johannes Huebl. Meanwhile, our refreshments on this early summer’s day include a Virgin Mary mix from Longbottom & Co, a company Mr Williams co-founded with another old friend, Mr Ed Bathgate. He’s particularly excited about the Virgin Mary, which was recently picked up by an airline. “I drink more tomato juice than any other drink when I’m on a plane, for some reason, so I’m excited to see how it goes,” he says. Perhaps unsurprisingly, Longbottom & Co already has the unofficial backing – immortalised on black-and-white video footage recorded on Mr Williams’ iPhone – of about half of the Hollywood A-list.

Mr Williams says he’s a firm believer in the law of attraction, which states that positive thoughts manifest themselves in positive outcomes: “If you tell yourself that you’re going to do something, the world will let it happen.” Of course, he acknowledges that it’s not quite as simple as that; you can’t just wish a happy and prosperous life into existence. It takes hard work, sacrifice and calculated risk, too. But the last few years have been tough for Mr Williams, both personally and professionally, and what he’s really trying to say is that he wouldn’t have any of this – the house, the family, the success – if he’d ever stopped believing in himself.

Besides, the events of the past year have seemed a little too neat, too perfect, not to suggest some sort of predeterminism or greater force at work. By way of example, he recounts the story of how he met his fiancée. Thirteen months ago, on the very same day that the builders left the premises after finally completing renovations on his home, he had a chance encounter with the person he would go on to share it with: the model, Ms Eliza Cummings. A few months later, she was pregnant; another two months later, they were engaged. A few weeks ago, their son, Wylder, was born. Now the sun is out, and the grass is growing just as it should. “We’re getting married at the bottom of the garden this summer,” says Mr Williams, gesturing to a quiet spot just beyond the lake. Everything seems to be in its right place.