The production, which opens on 17 April (previews from 22 March), is part of the World Shakespeare Festival and runs in rep until 15 September 2012.
Date & place of birth?
11 July 1978, Belfast.
What made you want to become an actor?
Bugsy Malone. I realised that you could do it as a job and it felt like I'd discovered a massive secret.
If you hadn’t become an actor, what might you have done professionally?
I never loved anything else half as much so its hard to say. I'd probably be staring out of a window somewhere daydreaming.
First big break?
I guess it was winning the Cameron Mackintiosh Scholarship. It covered my fees for drama school and contributed towards my living costs. I had absolutely no way to pay for any of it so it really did feel heaven sent.
Career highlights to date?
Playing New York in the summer of 2011 with the RSC ensemble - Dromio in Comedy of Errors, Orlando in As You Like It and Mercutio in Romeo and Juliet. New York is pretty wild. Well, it was last summer anyway.
Current co-stars excepted!... Matthew Evans - we worked together on four plays at the RSC seven years ago. We lived together, worked together and laughed so much together. He's in LA now but I visit him sometimes. He has a swimming pool and a car with no roof. This is what happens - your friends start leaving for America one by one. Mariah Gale - bloody genius.
What was the first thing you saw on stage that had a big impact on you?
Ha! Les Miserables! I saw it on tour in Dublin when I was 14. I just thought it was the best thing ever. I got the CD and tried to sing along in my bedroom, but my voice was never high enough. I strained and strained trying to stretch myself into a tenor. My voice not being high enough was worse than acne.
And the last?
Matilda. Pure, open hearted joy. Gorgeous and technically brilliant.
Where does Richard III rank in terms of Shakespearean roles?
Quite simply, there's lots of it and he is always busy. It's quite a lonely role and requires quite a lot of energy. You're pretty much on stage for three hours. Richard is a marvellous actor who falls apart. So does his kingdom and his play. It's a wonderful role and I don't feel at all "arrived" with it. I'm still exploring. He's a very funny and lovable creature.
You’re quite young compared to many Richards - how does this affect your interpretation?
I guess my Richard is pretty youthful. Immature maybe. Cartman from South Park is probably my strongest influence for Richard. I guess the link to him as a broken child is more evident.
What’s your favourite line in the play?
"I am too childish-foolish for this world."
And how are you tackling the infamous hump?
I have a hump that I strap on every night and do lots of yoga so I don't get injured by walking funny . Its a medium-sized hump, I'd say.
Are there any remaining Shakespeare roles you would particularly like to play?
Loads of amazing parts: Rosalind, Hamlet, Benedick...
What do think about Gregory Doran’s appointment?
I'm delighted for him. He is the most passionate, dedicated Shakespearean. I think he even looks a bit like Shakespeare...
What’s your favourite place in Stratford besides the RSC venues?
I love going for a run along the river. Oh and I love walking through Holy Trinity Church at night on the way home. That's where Shakespeare is buried.
Richard III is running as part of the World Shakespeare Festival - can you tell us more about that?
It's a celebration of Shakespeare as "the world's playwright" produced by the RSC for London 2012. Companies from all over the world will be taking part. I'm particularly looking forward to meeting up with the Brazilians and Iraqis when they bring their productions to Stratford.
If you could emulate anybody’s career whose would it be?
Bob Dylan. Cate Blanchett.
What’s your favourite film?
Back to the Future.
And favourite holiday destination?
What have you got lined up next?
I think I'll be working with Rupert Goold again after this.
Roxana Silbert's production of Richard III starring Jonjo O'Neill opens at the RSC's Swan Theatre, Stratford-upon-Avon on 17 April (previews from 22 March) where it continues in rep until 15 September 2012.