Twenty years as a jobbing actor, on and off, and Barry Ward could be forgiven for thinking it might never happen for him.

But next week the Irish actor goes to the Cannes Film Festival headlining one of the most anticipated competition titles, Jimmy's Hall. Directed by Ken Loach, it's the sort of flashbulb-popping moment that can make an actor's career. Just ask Peter Mullan, who won Best Actor at the festival for his turn as an alcoholic in Loach's 1998 drama My Name Is Joe.

This time, however, the spotlight looks set to be intensified with Jimmy's Hall, a 1930s-set Irish drama, expected to be the 77 year-old Loach's final feature film. Even on set, says Ward, the talk was of Loach retiring.

"As a lover of films, I found it very sad. We chatted about it a bit, and he gave his reasons. He seems to have his mind made up. But directors don't retire! They drop dead on set!" But is this really it? Ward smiles. "I like to think if a script landed on his desk, he wouldn't be able to resist the temptation."

Whether Loach does step down or not may well depend on the reactions to Jimmy's Hall, his eleventh feature-length collaboration with Scottish screenwriter Paul Laverty. The film follows Jimmy Gralton, an Irish Communist who became the only man ever to be deported from Ireland after he opened up a dance hall in County Leitrim, partly as a platform for his politics, causing huge consternation amongst government officials and the local Catholic priests, who considered it a breeding ground for revolution.

Such was the secrecy that surrounds a Loach project - actors are never given complete scripts - Ward was largely left in the dark.

"Until weeks after I'd been offered a job, I had no idea I was playing Jimmy Gralton," he laughs. Even his good friend Cillian Murphy, the Irish star of Loach's Cannes-winning The Wind That Shakes The Barley, was a little coy. "Cillian said 'I can talk about it until the cows come home but you should just experience it for yourself. But take my word, you'll love it - it'll be the best time of your life.'"

When he eventually did find out who he was playing, the 33 year-old Ward was left impressed by what he discovered about Gralton. "He has the courage of his convictions," he reasons, "despite threats and whatever and the challenge posed by other parties and the powers that were. He just had that compulsion; he was politically active and he was active in the community. He had such a big spirit. You can't keep that down. You have to share it, and it was infectious. Everyone else wanted to be around him."

What the film is not, says Ward, is an exercise in church-bashing - with Gralton more anti-authority than anti-religion. But Ward admits the religious aspects of the script resonated with him. "I had a very strict Catholic upbringing," he explains. "You take what you can from it, and you deal with it. And it wasn't as extreme as some cases: no violence or abuse. But we were regular church-goers and we'd prayed at home, sometimes, growing up. So you'd get all the propaganda and guilt and shame - that's certainly there."

Raised in Dublin, close to where his father and uncle ran a sawmill, Ward's initial interest was football, to the point where he came close to getting a trial for Ipswich Town FC. But it was not to be. "Then I started acting at 14 and things were going well in that and I lost interest in football." His career would be almost over now if he'd become a footballer, I point out. "And it's only beginning as an actor," he smiles. "There's a poetry to that."

His first job was Michael Winterbottom's 1994 Dublin-set television drama Family, scripted by Roddy Doyle. "Plucked from the street", he was still in his early teens when he was asked to go along to some open auditions. "I had no previous experience or desire. But it took off from there." Perhaps 'took off' is rather over-stating the case. Ward returned to school then went to college, only ever "dipping" his toe into the profession over the summer holidays. "I faffed around," he admits.

It was only when he landed a gig in 1999's American-set film Sunburn - alongside Cillian Murphy - that he began to take acting seriously. Murphy was particularly key in encouraging him. "He was like, 'You have to do this professionally. What are you going back to college for? Do this. You're good.'" Soon afterwards, he reunited with Winterbottom on his snowy drama The Claim, and it was enough to convince him to take up acting full time.

Even then he found it really hard to stay afloat, despite moving to London eight years ago. "I did all sorts of odd jobs. I don't think I acted for nearly two years and I was just trying to keep myself in London, so I was doing what I had to do to pay rent." Yet now it's all changed. Aside from Jimmy's Hall, he features in Bypass, the new film from acclaimed director Duane Hopkins (Better Things) and Blood Cells, a British road movie. "I'm almost down-and-out, an outsider living on the fringes of society," he explains of his role in the latter. After Cannes, the outsider may well be on the inside.

Jimmy's Hall premieres at the Cannes Film Festival on May 22 and goes on general release on May 30