The greatest challenge I've ever had as an actor.

The magic stuff was almost like light relief in a way, but of course it's also quite sinister, ... I learnt a couple of tricks, and I stole a line from a guy who was teaching me. He used to come in and do a few tricks for me, and he'd say 'I am magic!' You'll hear me say that in the piece.

Putting Katie in the box was really upsetting and difficult to film, but she was brilliant when we shot those scenes.

It's quite a tragic story from Bernie's point of view too, because he is a massive fabricator of reality.

Of course the subject matter is controversial, but I decided to do it because I really respect the people behind it, Company Pictures, who've made great television like The Lakes and Shameless, ... It's very dark but it's not gratuitously violent, or exploitative; it's been made responsibly, not sensationally.

He's a monster - and that got to me.