For you, what's at the heart of "Half-Blood Prince?" What's at the core of the story?
RADCLIFFE: Paranoia. There's a very strong scene in the film that's all about Harry's increasing paranoia about Draco Malfoy becoming a member of the Death Eaters. Also, it seems a big part of all the films, but death. We're even closer to it in this one because Dumbledore is dying and knows he has to die. And the image of this old man knowing all that is a very, very sad one. But he carries on anyway. He doesn't give up and he absolutely fights until the last minute.

This film had a mixture of both adventure and some more intimate moments. Which are your favorite scenes to play? Do you like the action or the quieter scenes?
RADCLIFFE: I think that I like the quieter scenes. There's a lot of action but the quieter scenes will, generally speaking, be where the heart is. That's not to say there aren't some emotionally quite intense action sequences, but when there are just two people sitting down talking the stakes are very much higher, emotionally. My favorite scene in the film, actually, is one that I'm that not in, which is probably not that surprising because I hate watching myself. It's with Rupert (Ron) in Quidditch practice, and it is genuine laugh-out-loud funny. And I don't laugh out loud that easily.

During the beginning of the series you had the consistency of Chris Columbus directing both the first and second films, but then new people came in for four, five and six. What's the difference between working with a new director on each film and working with "Half-Blood Prince's" director David Yates, who will ultimately be on four films in a row?
RADCLIFFE: When a new person comes in it keeps you on your toes. I think in the younger years it was very important that we didn't get complacent, and I think having different directors helped in that. But the great part about the consistency of using someone like David–and David's on his third now, he's doing the one we're filming at the moment–is that we just know each other very well, professionally. We know how the other wants something to be done and we're very good at communicating with each other now. And we always were with David–and to an extent all the other directors, they've always been really communicative–but with David sometimes nothing needs to be said. I'll get to the end of the take and I'll say, 'Oh sorry, that was crap and let's go again' immediately because I know what I did was not what David was looking for.

In the future, when you look back at the making of the six films, what do you think might stick in your mind about the process?
RADCLIFFE: Michael Gambon, when we were doing all these sequences together, would come up with abbreviations for the shots. None of which I can actually repeat because they're all quite offensive, but they're very, very funny. Some of them have actually stuck on the Potter set.

One of the sequences, on this last film, was with Tom Felton as Malfoy in the bathroom. Me and Tom have always liked each other but we actually started getting on really, really well in the last film, so that will be one of the binding memories.