After an initial period of cold feet, he took to the Potter universe, he says, like a duck to water. His television work might be on a human scale, but he grew up wanting to be Steven Spielberg. Yates says he adored the film's visual challenges, from the look of the sort-of-equine, sort-of-cadaver Thestrels to the brilliantly lit Room of Requirements, where Harry trains his rebel army at Hogwarts (this particular set, which required under-floor lighting, was described by Radcliffe as one degree hotter than the sun ).

In eight weeks' time, Yates will begin filming the sixth in the series, Harry Potter and the Half-blood Prince , which he describes as the sex, drugs and rock 'n' roll instalment. The drug is Liquid Luck, a feel-good potion that sounds like a supernatural version of ecstasy. In the next movie, Yates - who is invariably described as an actor's director - will be reunited with a cast that seems to include every serious actor in Britain, from Maggie Smith and Michael Gambon to Gary Oldman and Emma Thompson.

If they all decided to declaim at once, they could probably bring down Hogwarts. It seems that the director thinks Radcliffe may one day hold a place in the pantheon - especially if he keeps perfecting his craft through hard work. Yates is known for driving his actors, politely and quietly, until they've given their best.

Radcliffe's kissing scene with Katie Leung, who plays Cho Chang, reportedly took more than 30 takes. The director prepared his young stars by first asking them to share stories of their first kisses - he shared, too, like a good leader - and then clearing the set for the actual shot. What's lovely about Dan, says Yates, is that after the 14th or 15th take I'd say, for whatever reason, We have to go again, Dan.

' And after four or five weeks he'd turn to me and say, I think I need to go again.' Downstairs at Claridge's, the hotel where the stars have gathered for their press conference, Radcliffe remembers it from a slightly different perspective - more from the worker-bee's angle: David would come up to me after a take and say, That one was good, but it wasn't real.' There were times when I thought he said, theatrically tearing at his hair.

But in the end I could. Radcliffe is, perhaps thanks to seven years in the limelight and the adulation of a million girls who would do anything for him, seriously charismatic: handsome, eager, self-effacing, good with a one-liner. Watson is dressed in a revealing black gown that causes a middle-aged journalist to gasp, rather creepily, Did you get a look at that dress?

It's easy to forget she's just 17, what with that dress, but then there's her hyper-articulate speech and the endearing geekiness. Asked what she's bought with her star's salary, she responds that her Apple computer is her pride and joy. The third of the trio, Rupert Grint (who plays Ron Weasley), is the one who seems most authentically a teen, with his fall of red hair, his collapsing posture and his Sex Pistols T-shirt.

He reveals that he's recently bought a working ice-cream van - toppings and all - and hopes to continue acting, but if that doesn't work out, you know - ice-cream van. Radcliffe clearly rules the room and handles most of the questions: Did Harry influence his own character over the years? (Not so much.

) What will he do after these films? (More acting, and write poetry.) Does he take fictional characters, such as the tormented Alan Strang in the play , home with him at night?

( It's very important to leave Alan Strang in the theatre. As Strang in , which ran on London's West End this spring, Radcliffe famously appeared naked on stage in front of nearly 1,000 people a night. After an initial period of cold feet, he took to the Potter universe, he says, like a duck to water.