Look at David Heyman’s CV as a producer on IMDb and you’ll notice that the top half is both dazzling and diverse: there’s the forthcoming CGI Paddington movie, JK Rowling’s new Harry Potter spin-off, two heavyweight BBC films with David Hare, and another project with Alfonso Cuarón, for whom Heyman produced the brilliantly intense space drama Gravity. The film has already done well in the American Critics’ Choice awards and will surely be in Golden Globe and Oscar contention for best film, best director and best actress for Sandra Bullock’s performance as the drifting astronaut, Ryan.

‘One of the things I love about Gravity is that it is an immersive film — you are there with Ryan in space — and it’s a privilege to work with Alfonso,’ says Heyman, a trim and startlingly handsome 52-year-old Londoner, with a deep-graven face and solemn grey-blue eyes. ‘But there are a lot of good films out there from the major studios, from American Hustle to 12 Years A Slave.’ He takes a sip of green tea, unbothered by the heat of the log fire in an upstairs room at Blacks private members’ club in Soho. He’s off on holiday to Brazil after our meeting: ‘a reward for a year of no sleep and no break.’

The bottom end of Heyman’s CV, which lists his work in the 1990s, is not so hot. Blind Justice? Ravenous? No, me neither. The years from 2001 to 2011, of course, are dominated by his eight-picture cycle of Potter movies adapted from Rowling’s novels. The films never won a single Oscar, but are nevertheless an unparalleled cinematic phenomenon, making over $7 billion in cinemas, the same in book sales, and are estimated to have made the same yet again in merchandising.

‘I was incredibly fortunate,’ says Heyman. ‘But I’d rather be lucky than good.’ The oft-told tale bears quick reiteration. After some years as a junior studio executive and a struggling producer in America, Heyman had returned to London in 1996 with a ‘very basic’ deal with Warner Bros, giving the studio first refusal on any British books he found that could be turned into films. He hired three people: one of them, Tanya Seghatchian, read a trade article about a forthcoming novel about child wizards and ordered it. Another, Nisha Parti, read it and recommended it to Heyman.

He read it, loved it and thought it ‘might make a modestly budgeted British film’. Warner took a punt because he hadn’t come up with anything else so far. He repeats his point about luck: ‘If I had come back six months earlier in a different frame of mind, if Tanya hadn’t read the article, if I had been in a bad mood when I read it and decided I didn’t like it... there’s so much that could have affected it. I was in the right place at the right time.’

Once the first film came out, though, I say, your life must have changed instantly in terms of influence and income. Did it make you tons of money? ‘Not instantly,’ he says. ‘Until the end of the third Potter movie I was living at my sister’s, in a 6ft x 8ft room.’ That has changed now. Heyman has been married for seven years to the interior designer Rose Uniacke: they have a five-year-old son, Harper, and a wider family that embraces her three children and stepson from her previous marriage to Robie Uniacke (who now has a son with the actress Rosamund Pike). ‘My wife has an antiques shop on Pimlico Road and she designed our house and made it very nice,’ he says. This is modesty: Rose’s clients include the Jo Malone HQ and numerous high-net-worth individuals in London; their house in Pimlico is reportedly worth £11 million, and includes a swimming pool, winter garden and ballroom. ‘In classic male-provider terms [Potter’s success] means I live in a nice house, I have a big family, school fees are not an issue,’ he says. ‘It has changed my life in lots of ways, but one thing it has done is bought me time. I can work on things I really care about. I still struggle to make the films I want to make. People still turn me down. But I have access. People will listen because they don’t want to miss out on the next Potter. Although I’ll never find the next Potter because Potter is a once-in-a-lifetime thing.’

The franchise also taught him ‘how to produce films of scale that are technically complex, and how to work with a wide variety of top, brilliant film-makers’. He sees the work of a producer as creative rather than merely facilitative or financial and is proud the films have ‘an overall architecture, which comes from Jo [Rowling], which I helped maintain, but each director’s film is their own’. The greatest gift it brought him, though, was relationships. As he points out, most movie crews are like a family that breaks up after an intense year together. But over 11 years of Potter production he witnessed ‘children starting out at nine and ending up at university; births, marriages, deaths, the whole cycle of life’.

He chaperoned Emma Watson to the Potter premieres and will soon start work with her on another book-based fantasy saga, The Queen of the Tearling. His relationship with Rowling was based on trust and mutual support: when he asked her for more detail on Sirius Black’s background for the third film in the series, she faxed back an entire family tree half an hour later. Thus he will produce her Potter spin-off Fabulous Beasts and Where to Find Them (but will leave the recently announced West End musical to Sonia Friedman). Paddington, in which Colin Firth voices the beloved bear, ‘may be the most oversupervised film for visual effects in history’, with veterans of Gravity and four Potter movies working on it.

Heyman’s relationship with Cuarón began when he helmed that third film, The Prisoner of Azkaban, and the director is now godfather to Heyman’s son and ‘someone I could turn to if I was in trouble’. They will work together a third time on a film entitled A Boy and His Shoe, after the success of Gravity, which Cuarón brought to Heyman as a fully formed vision with huge technical challenges. ‘It was great to work on an immersive, grown-up film that worked critically and commercially,’ he says. ‘I hadn’t really worked with stars like Sandy [Bullock] and George [Clooney] before and I understand why they are stars because of how they manage every step of the process.’

Bullock had to act, usually alone, in a helmet, using mostly her eyes, and keeping all her muscles relaxed as they would be in space, as a two-ton camera zoomed to a stop inches from her face; then she had to fly all over the world and gallantly answer questions about whether she fancied Clooney or not. ‘She is one of the hardest-working people I have met in my life: her commitment and discipline are extraordinary,’ Heyman says. ‘I think she went out for dinner once during four or five months of filming here. Alfonso Cuarón, excuse my French, is f***ing rigorous and demanding. It’s hard work, being him or producing him.’ He insists the veneer of glamour that surrounds film is just that, a veneer. Mostly, it’s hard graft. For his own part, he rarely goes to parties and premieres (‘I might have been more of a networker before Harry Potter, when I was single’) and his only indulgence is travel.

Film was the Heyman family business. His father John was an agent who in his time represented Elizabeth Taylor and Richard Burton ‘who were sort of godparents to me’. John later became a producer and pioneered different structures of film financing. David’s mother Norma had been an actress but became a producer of films such as The Honorary Consul and Dangerous Liaisons.