More common than those sensational downhill trajectories into rehab or prison, however, are the child stars who quietly fade away as adulthood encroaches, fodder for endless "Where are they now?" articles – the Fred Savages, Mark Lesters and Peter Ostrums. As a lad he played Charlie Bucket in the 1971 film Willy Wonka & the Chocolate Factory, but is now a successful equine vet working in upstate New York.

Playing the obsessively house-proud Mrs Potter, polishing and cooking her way into the marital bed, is Helena Bonham Carter – the third time the actress has portrayed Highmore's mother.

"She's my stepmum this time," corrects Highmore, who had filial roles opposite Bonham Carter in his debut film, Women Talking Dirty, aged seven, and again in Charlie and the Chocolate Factory. Obviously, when you get on so well with someone and then you have to dislike them on set..." Bonham Carter is part of a tight web of associations for Highmore.

They didn't really see you differently; it was like you'd gone away on holiday or something." Highmore was a hard-working scholar, unlike the character he plays in his next film, Homework, which was shot earlier this year in New York, where he shared a rented apartment with father.

("We had cooked meals instead of room service, which was great," he says, a sentiment I suspect few chaps his age would share.) In this coming-of-age drama co-starring Emma Roberts (Julia's niece), Highmore plays a high-school slacker who strikes up an unlikely friendship with a girl he has admired from afar.

' It would start off like that," he says of the casual nature of his early work.

Things became a good deal more serious with Finding Neverland.His latest transitional, not-quite-adult role will be screened on BBC1 over Christmas.In Toast, an adaptation by the Billy Elliot writer Lee Hall of Nigel Slater's memoir of family and food in the West Midlands of the 1960s, Highmore plays the future cookery writer from his mid-teens through to catering college.Slater's enjoyable autobiography is almost Proustian, if you substitute Jammie Dodgers for madeleines; it tells, through the cooking and confectionery of the era, the story of his mother's premature death and the takeover of the family home by the cleaner – and soon-to-be stepmother – the hostile Mrs Potter.It's a not-altogether-lost world of what are now no doubt retro-chic victuals – salad cream, beetroot in vinegar, Angel Delight, Spangles, Sherbet Fountains and bars of Caramac."It is very funny to go through your life with her as your mum every so often. The actress is married to Tim Burton, who is supposed to have cast Highmore in Charlie...