“This is my favourite of the films,” says Felton, as cheery as Draco is sneery. “The first one I’ve worked on from beginning to end, not just a month here and there.”

Felton’s big moment comes when he and Radcliffe square up for a scrap that plays like something out of Bond or Bourne. “It was great,” raves Felton.

“We spent a week in this misty bathroom set, rolling around in the water having all sorts of fights. It’s a longer sequence than it is in the book.” There’s blood – but also some fleshing-out.

“This film develops the character further than before,” he says.“We take the chance to explain why he’s such a complete cretin, that he’s not just doing it for the sake of it.”