So, Harry Potter. How did you become involved with the films, was it through the audition process?
It was an audition process, yes. I’d had my ear out for a while, because I’d read the book and thought that it could be really good. And when I heard that they were doing it I knew that I had to get on to this. So the agent said that I had an audition, I prepared well for it, went in and did it.

It was a great experience, I had lots of fun with it, and I came away with a good feeling. But sometimes, in an audition that’s not really a good sign. I’ve often done that and thought ‘Yes, yes I‘ve nailed it,’ and then you don’t. And other times I’ve come out a bit anxious and I’ve got it.

So three weeks went by, and then I heard that ‘Yeah, you’ve got that, and you’ve got that as well’, I had two parts. But then, at that time, little did I know that it was going to become a part of my life for 10 years. It was 2000 then, it’s now 2010, and I’m still doing it. I still will be doing it until June.

How did you feel about the decision to split the final two films?
I think it was good, because I think sometimes in the past we could have done that with the other stories, because they are so rich. I’m never actually disappointed… well, I am disappointed because sometimes it leaves my parts out… but I think the readership is sometimes disappointed. They’ll read in their minds, and in the later books certainly, you were starting to think ‘Ooh, I wonder what this is going to look like in the movie, I bet this will look fantastic’ and then when certain sequences weren’t in there, there was possible disappointment.

So I think it’s a really good decision, because we can do justice to what is the last book and what is the finale of, if you take it as a whole saga, the end has to build, do you know what I mean? I don’t remember a point in the films though, where we knew ‘Right, now we’re going all the way’.

I just remember each time we were finishing, we were wondering if we were going to be back again. If I’d have known 10 years ago it would have been lovely. Because as an actor, you really live day-to-day, you live by each job you do.

And my theory of really keeping my feet on the ground is to say that there is no rule to say a producer will use me again in a film. So I look at this job that I’m doing and relish it, because it may well be my last. Because who’s to know?

It keeps you grounded, it keeps you humble, and it keeps you doing your best work, because you know that you’re only as good as your last movie. Val Kilmer said that once, actually, when he was disappointed because one of his films had flopped.

One thing that you never rush in movies is make-up, as I was reminded painfully on my next big shoot - Harry Potter And The Philosopher's Stone. I had two parts - Professor Filius Flitwick, a teacher at Hogwarts, and the goblin bank teller.

The make-up took four hours to put on and an hour to take off. I had to be at the studio for 4am to be made up and in costume for a 9am shoot which could last for up to 12 hours.

Little went wrong during filming, although I was involved in one small incident during Goblet Of Fire. Snape, played by Alan Rickman, reveals the goblet to the pupils by magically whipping the cloth away and into the air. This effect was achieved by firing air through pipes behind the goblet, which shot the cloth skywards.

It worked perfectly first time, except that the cloth landed across my face. Everyone tried to finish the scene but we gradually disintegrated into giggles. Even the usually sombre Snape cracked a slight smile.

During one long night shoot, I sat and chatted around a tiny heater with Alan, Maggie Smith (Minerva McGonagall) and Michael Gambon (Albus Dumbledore). 'What do you think of these beards, Warwick?' Michael asked. 'Well, they're a bit of a pain.' 'They most certainly are, these wisps get everywhere.

If I use my arms and wand it always gets entangled, and I yank the thing off my face. And dinner is a nightmare.' Despite a career working with some of the world's biggest film stars, I hope that I've always managed to keep things in perspective.