"Unfettered fun" is how Isaacs describes the experience of playing the Malfoy. For a moment, he talks about Malfoy's focus on "racial purity - it sounds like right-wing political campaigning," but then he says, "I don't want to look at the serious side of it. It was too much fun. It was an opportunity for me to play like my kids play, and to chew up the scenery with some of the greatest actors in the world... They prove that it's not true that an unhappy film set makes for a good film...

"We had a ridiculously good time making them," he says, recalling specific scenes with Richard Harris, Robbie Coltrane, Ralph Fiennes and, of course, Harry himself, Daniel Radcliffe.

Talking about how the last book is set to be made into two films, he says ominously, "I think that's a mistake."

After a beat, he adds, "It should be made into 10 films so I can do it for the rest of my life."