Hugh O’Conor was just ten when he starred in Lamb opposite Liam Neeson, and only fourteen when he played a young Christy Brown in My Left Foot, starring Daniel Day Lewis. He also starred in commercial hits such as The Three Musketeers, opposite Charlie Sheen, Tim Curry and Kiefer Sutherland, and Chocolat, featuring Johnny Depp and Juliette Binoche.

But these days, O’Conor is more focused on writing and directing. Aside from filming gorgeous music videos for I Draw Slow, The Hot Sprockets and Heathers to name but a few, the multi-talented Dubliner is developing an animated feature and two TV shows. But when it came to starring in The Stag, John Butler’s light and sweet comedy about Irish lads on a bachelor party, O’Conor found the decision easy. Possibly because he didn’t entirely make it himself.

“I didn’t have a choice!” he jokes.“They’re my friends, they blackmailed me! I went over to visit John Butler in Budapest the summer before last, and I knew he was writing something with Peter McDonald, and they just kept laughing at me! They kept taunting me saying: ‘We’re going to write this thing for you, we’re going to make you do this!’ Which was mildly terrifying.”

O’Conor plays Fionnan, the mild-mannered fiancée of Amy Huberman, whose friends pressure him into embarking on a weekend stag party. When Peter McDonald turns up
as Amy Huberman’s loud, brash, impulsive and mildly psychotic brother, the stag goes on an eventful detour, with electric shocks and rampant nudity along the way. But though it’s being billed as the Irish Hangover, Butler’s film is a sweeter, more emotional affair.

“We liked the idea of exploring male relationships and insecurity about friendship, because there’s something innately strange about a forced gathering in exclusively male company. Because men – particularly Irish men, maybe – are amazing at talking to each other but never actually saying anything. We do that very well.

“So it’s a lot of fun, but there are also moments where you see our characters unwillingly open up. I think the writers took little moments and experiences from all of our lives – for example, Peter has been attacked by a dog, which turns up! But we’ve also all had fucked-up relationships, and we address the recession, and there’s a huge part of the film about fear and insecurity and the ridiculous excuses we use to get out of relationships.”

The film also stars Andrew Scott, who’s experiencing an unprecedented level of fame after playing Moriarty in BBC’s series Sherlock, and O’Conor laughs about his friend’s tales of getting fan fiction from obsessive fans. The two actors were in school together, and Scott has joked in interviews that he was always jealous of O’Conor’s early success – but O’Conor laughs this off.

“Even with My Left Foot, the lads in school didn’t give a shit! The only thing they cared about was when I was on The Late Late Show, so they cornered me in the yard and said: ‘You better say ‘hi’ to us!’ So there’s this clip of me on the show, nervously saying to Gay Byrne ‘and I want to say hello to all my friends in school’ – just so I wouldn’t get beaten up the same day!”

The actor, who is extremely self-deprecating and very dismissive of the notion of fame, is proving pretty canny when it comes to using his work to further good causes. He starred in Domhnall Gleeson’s hilarious sketch series Immaturity for charity and has directed ads for Parkinsons Ireland.

He also starred in a commercial promoting marriage equality in Ireland, which is going viral again in light of the recent public discourse about homophobia and equality. It shows O’Conor asking random Irish people for permission to marry a woman called Sinéad, ending with the tagline: ‘How would you feel if you had to ask four million people for permission to get married?’ It’s a beautiful and smart way of addressing discrimination, and the actor is delighted that it’s resurfaced.

“It’s pretty amazing. It’s a version of an American ad that we shot about five years ago, and it went viral then, too. So Panti Bliss tweeted it the other day, which is really nice that it’s being used in this really important public conversation. And I think it’s clever too in that it’s from a straight person’s point of view, so it highlights just how horrible discrimination is. If it can do any good, I’ll be thrilled.”

The Stag will be the closing film at this year’s JDIFF, and goes on general release on March 7.