“It’s just projects like this one that give me so much joy,” he enthuses, “where I turn up on set and really don’t know what on Earth is going to happen from one day to the next. Obviously, I knew I was playing a dead person, but there’s a lot more to it than that. I don’t want to say too much about the plot.”

“I would absolutely, definitely do a blockbuster again,” he says enthusiastically. “Of course I would! It just has to be a good one, a great script.

“I don’t know where people get this idea from that big movies can’t be as much of a challenge as an independent film. They can be really hard work. Harry Potter just got better and better as a franchise and I am still so proud of it. I would definitely do big-budget films again, just give me one worth doing.”

Recently tipped to play Lee Atwater in John Krokidas’s comedy Young Americans, about a young Karl Rove (George W Bush’s former senior advisor), the actor now says “the film may not happen”.

“Alan was extremely kind, generous, self-deprecating and funny”.

“I just feel that it needed to be said,” Radcliffe said. “He was just such an important man to me, not just as an actor. He came to see everything I ever did, he was an incredible man and friend. It’s just a huge loss to all of us.”