The theatre director was a young idealist, and he wanted to change the world.

He brought his theatre group to a rural village, where the people were mired in poverty. In the village square, they put on a play.

It was a simple fable of how the rich oppressed the poor. The village audience was roused and inspired by it. And then came the play’s turning point. The hero – a poor man – was being beaten down by the rich man. The director stopped the play, and turned to the crowd.

“What should the hero do now?” he asked.

“Revolution!” cried a man in the audience. “Revolution!” the others cheered. They started to run around the village, seeking weapons.

The actors were aghast. The director was terrified. Hastily, he tried to explain that that wasn’t quite what he’d been thinking of. His group abandoned the play, and bid a hasty retreat back to the safety of the city.

The theatre director was a Brazilian named Augusto Boal, and he went on to become perhaps the most influential voice in “activist” theatre in the world. After his humbling early experience in rural Brazil, he came up with a careful new system. He called it “theatre of the oppressed”. It was a way of using theatre to explore the problems facing people, and help them find practical solutions.

Boal visited Ireland often, leading workshops with theatre folk and community workers; I interviewed him in the late 1990s. He died a year ago this month. His legacy lives on, though, and last week, his theory was put to the test in Temple Bar.

That may not be an obvious site of oppression. Eustace Street, though, is home to a café and day centre run by the homelessness charity, Focus Ireland, and it was there that the theatre company Gúna Nua chose to debut their first venture into Boal’s “forum theatre”.

It wasn’t much of a play, in the conventional sense. There was no set, except for a few ordinary chairs. The actors competed with the noise from the kitchen behind. People wandered in late, or got up during it and went out for a smoke. This was as far from the bright lights of Broadway, or even the bohemian cool of the London, New York and Edinburgh fringe scenes, as it gets.

Which is why it was intriguing that the company involved was not simply a group of well-intentioned volunteers, or low-key community arts workers. Gúna Nua is one of the most successful small Irish theatre companies of the moment, and this venture was sandwiched neatly between runs of their international hit play, Little Gem, by Elaine Murphy.

If Gúna Nua seems, at first glance, an unlikely company for this ground-roots political theatre, writer Gerry McCann admits he was an unlikely candidate for playwright. An actor by profession, he had grown “very cynical,” he says.

“Acting grinds you down. You just want to make a living.

“If I’d met somebody before doing this who’d told me they were in a play for homeless people and drug addicts, I’d have thought they were daft.”

But Gúna Nua was interested in trying out Boal’s method, and they offered to send McCann, and another company regular, Jenny O’Dea, to London for a weeklong training.

For McCann, the enthusiasm and innovation he encountered was a revelation. He and O’Dea came back “fired up”, and Gúna Nua moved quickly to develop a production, finding a willing collaborator in Focus Ireland.

In the café last week, the small cast tripped lightly through a short play about a teenage girl who gets pregnant and is thrown out of home, and then one about a pair of drug addicts on a recovery programme who fall for each other, and compromise their recovery. Both were tragi-comedies, in miniature, with sad endings.

Afterwards, the audience were asked to suggest where the characters could have made different choices, and then asked up to improvise scenes with the actors.

One man found himself playing the part of the addict wrestling with the conflict between his recovery and relationship.

“We’ve lied all our life,” he said, to the gorgeous young actress opposite, Charlene Gleeson. “Lying got us into drugs. If we tell more lies we’re going back.

“I love you, but I don’t want to tell lies and wreck the whole lot.”

He acted simply and unselfconsciously, improvising with searing honesty. As raw drama, it was mesmerising. As an act of political theatre, it was potentially transformative.

“I’ve seen my best of mates dying of overdoses,” he said, afterwards.

It would be glib to suggest that an afternoon of theatre can prevent that. Gerry McCann explains its intent in more modest terms.

“It helps you to think in terms of options and choices, in a situation where you may think you don’t have any options, where you feel trapped.”

But it’s not just about “helping”. For Paul Meade, Gúna Nua’s director, this experiment will feed back into the company’s mainstream work, lending it authenticity and urgency.

They’re two of the qualities that their hit play, Little Gem, has in spades. For Gúna Nua, the synergy between political theatre and popular theatre could yet prove a fruitful one.

Little Gem returns for a further national tour in the autumn. See