Great British actor Gary Oldman, known for roles like Dracula, gets his teeth into playing everyone's favourite convict, Sirius Black.
He tells Lizo what went into his performance in The Prisoner of Azkaban.
Lizo: You bring such energy to the character of Sirius - where does that come from?
Gary: I dunno! Well, Alfonso the director I think. He has such enthusiasm and a joy for life - I'd say in this role that's where the majority of it came from.
And this role - it demands it - the passion and the energy is there in the book and the script.
Lizo: Did you read through all the books, did JK give you advice?
Gary: I read the third book. I'm now finding out stuff in the 4th and 5th book that I wish I'd known! I just basically read the third book - that's the key that unlocks the part.
Lizo: He's a complex character - how do you play a character like that
Gary: Psychologically he's very complex. That was challenging. It's a bit like Shakespeare - when you have dialogue which is also plot it's quite challenging.
I was surprised by how difficult it was to pull off.
Lizo: What was it like working with the kids - they've not done as much work as you?
Gary: They're such a part of this world that's been established and they've got two movies under their belts already - they're seasoned pros by now!
Lizo: Did you have an input into how Sirius looks in this film?
Gary: Yeah, a little bit. I had long hair and a beard and I thought it's a look that we could possibly go with and I turned up.
In terms of costumes I mean it's limited - I wear a prison outfit, I've escaped. But a lot of the look, the tattoos and things was Alfonso.
Lizo: Your back in film five is that right?
Gary: I'm briefly in four and I come back in five. So I've got a career!