How did “Peddling” come about?

I didn’t really have any intention to write. But I met this boy when I was eight years old, and he stuck with me, and I’ve had a desire since I was about 16 to remeet him.

We used to get a lot of door-to-door sales boys where we lived in Mill Hill [in North London]. Sometimes we bought something, sometimes we didn’t, and on one occasion we didn’t and the boy that got turned away just lost it. He camped outside for hours, throwing stones and his basket. Eventually we had to call the police, and he left before the police came. Where did he go? What made him do that? I’m sure these questions weren’t really swimming around in my head at eight, but they stuck with me somewhere.

"Peddling" is the first play you’ve written, but it’s also your first time performing a solo show. How does the experience compare to ensemble work?

You’ve got to be available to surprise yourself, because that’s the only thing that’s going to happen. Before you know it you’re stuck in a rut—especially because there are so many rhymes and the rhythm is so particular, if you’re not careful you just play the rhythm, the rhymes. So it’s almost about tripping myself up on purpose.

You began your acting career in film, but have played mainly theatre roles since then. Was that always the plan?

I knew it was always something I wanted to do, ever since I was really young. I saw my uncle [the actor David Troughton] in “The Tempest” and I was like, “I’m going do that, I’m going be on stage and make people feel the way I’m feeling now.” I feel very comfortable in the theatre and my most brilliant experiences of art have been works that I’ve seen in the theatre.

Are you ever tempted to compare your path to that of your “Harry Potter” co-stars?

I’m aware of them and I’m very happy they’re doing what they’re doing but I wouldn’t compare myself to them. I don’t feel jealousy or anything like that really, because they’re just different situations. I’m not one of “the three” [the trio of young actors who starred], so I’m not going to be in that position, but equally, that allows me to get on the Tube.

The thing with [having played] Dudley is that you get a call every now and again going, “We’re looking for a really fat, rattish guy.” And then my agent has to go, “Oh no, sorry, he’s changed.” And so I think that if my career was going to take off, it would take off in that sort of way. I had no desire for that to be my career, or to be my life, and to cash in on that. It was completely against everything that I wanted to be. My measure for fulfilling my ambition has always been the roles [I’m playing]. That’s the only thing to go by really. When that notion of career takes over the notion of why you’re doing it in the first place, that’s when it gets dangerous.

"Peddling" is at the Arcola Theatre, in London from March 4th-28th 2015