DAVID HEYMAN carries the weight well. Even if you look hard, scrutinise his every move from a short distance for a couple of hours, you don’t notice that it’s right there on his shoulders.

Heyman sits in a café at eight in the morning and laughs, tells jokes and sips tea with about as much angst as a sailor on shore leave. But there is, unmistakably, a great load to carry. For Heyman, 42, is a producer of films that millions of children around the world love, and love to pick over in detail to see whether the tales remain true to the books. The books, of course, chronicle the life of a young wizard called Harry Potter.

Two films down, with $1.8billion (£982 million) in box office takings to date, and Heyman’s on a high.

But there are as many as five to go, including one this summer. A false move and vengeance will be rained upon Heyman from an army of pre-pubescent bookworms. He would never be able to walk safely through a playground again.

Heyman is aware of the risks. “When you’re cutting an entire novel into a two-hour film, there have to be edits, and sometimes the author needs to be open to adaptation. They are giving up a certain aspect of control,” he says.

But he has never considered deviating from the course laid out by J. K.Rowling, the creator of Harry Potter. Indeed, she has been given the freedom to exert perhaps more influence on the Potter films than is usual when a book is adapted for the screen.

The storyline of the Harry Potter films is one thing, but the look and feel of a film are different beasts again. The appointment of an unexpected director, Alfonso Cuarón, responsible for the critically acclaimed Mexican film Y Tu Mamá También, to guide the third instalment prompted a chorus of whispers in classrooms the world over.

But Heyman, who is busy finishing the third of the series, Harry Potter and the Prisoner of Azkaban, and simultaneously starting pre-production on the fourth, The Goblet of Fire, is relaxed: “The best and most successful films come from taking a risk.”

For now, at least, Heyman is bearing the yoke of responsibility with ease, and the kids can empty their pockets of stones. On the other shoulder, meanwhile, sits the weight of expectation. This has been placed, perhaps unfairly, by the cynics who might say that Heyman’s career as a player in the film industry comes down to two curiosities: the luck of hitting the mother lode with the Potter books, and the door-opening ability that comes with being part of a highly distinguished showbiz family.

John Heyman, his father, was an actors’ agent before producing a succession of big films and pioneering methods of film financing, while his mother, Norma Heyman, was a successful actress turned producer whose famous parties were attended by friends such as Elizabeth Taylor and the Oliviers.

The expectation comes from this question: what is Heyman going to do next that proves he isn’t some well-connected guy who simply got lucky?

With a smile, Heyman begins by explaining that his career extends well beyond the moment he decided to buy the Potter film rights, and includes almost two decades in Hollywood as a producer and studio executive.

True, his first job was as a runner on A Passage to India, which his father helped to produce. But after that he went to Harvard University, and then packed himself off to Hollywood where he vaulted past other aspiring players to become a creative executive with Warner Brothers, working on films such as Gorillas in the Mist and Goodfellas. His meteoric rise continued into the late 1980s when, at age 26, he was made a vice-president of United Artists.

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