HOW much does an actor need to know about playing a real-life character before taking on a role?

In the case of Brian McCardie, set to play Scots-born revolutionary James Connolly - one of the key figures in the Easter Rising in Dublin in 1916 - quite a lot.

Carluke-born Brian, who made a career-changing appearance as Rob Roy’s brother in Michael Caton-Jones’ 1995 film, reveals he has read an incredible 53 books about the man.

“I knew very little about him,” he says of Connolly, before the journey of discovery.

“To be honest, I didn’t even know he was Scottish. But the more I learned about him the more fascinated I became.”

Connolly, the son of Irish immigrants, grew up in abject poverty in a Edinburgh’s Cowgate. His desperate life forced him into the British Army, at the age of fourteen.

However, as the teenager grew his socialist ideals formed, he came to hate the army and deserted. Later, he emigrated to Ireland where he worked as a trades unionist.

After spending time in America, and in the process becoming even more politicised, James Connolly returned to Ireland in 1910 and helped form the 200-strong Citizen Army.

It was almost inevitable he would become part of the rebellion of 1916, and he was in fact badly wounded in two separate attacks.

The Easter Rebellion failed and the ringleaders sentenced to death.

On May 12, 1916 James Connolly was executed by a firing squad while strapped to a chair at Kilmainham Gaol.

“It was never a Catholic-Protestant thing for Connolly, it was about changing the world for the better,” says Brian, who has appeared in River City and more recently in Outlander.

“It was about improving life for the working classes. He hated ‘kings and kaisers and capitalists and bankers’. “And what I learned was he had had seven daughters and was determined they should be treated as equal to men. He was a strident feminist a hundred years ago. Clearly, he was a man ahead of his time.”

Connolly, written by Brian and his brother Martin, is set on the eve of the 1916 Rising, when James Connolly is barricaded within the GPO Building in Dublin.

This one-man play explores Connolly’s life as a revolutionary, poet, union organiser, author, publisher, international socialist, feminist, Irish freedom fighter - and martyr.

“Connolly was a fascinating man,” says Brian. “He left school at ten, but was determined to educate himself. When he went to New York for a time and taught himself several languages including French, German and Yiddish, to be able to communicate with the working classes.”

This isn’t the actor’s first incursion into the mind of the Scottish revolutionary. This year, Brian starred as James Connolly in Rebellion, the RTE drama series which tells the story of the Easter Rising via three young women’s personal tales.

“When I read up on James Connolly I came to understand the man. And when we were making Rebellion we had a Finnish director who wanted to change a few details for the sake of a storyline but I found myself saying ‘No, you can’t say that because it wasn’t true.’ Thankfully, I was able to have my way.”

Brian admits he feels a special connection with Connolly. In fact, when he first tried on the uniform for the TV series, his eyes welled up. “I even looked like him,” he said. “And I could understand his determination, his sacrifice, to change the lives of the working classes.”

There’s little doubt Brian McCardie’s Connolly will be played with weight and integrity. The actor has long attracted critical claim since his stand out appearance in Rob Roy, revealing huge intensity in drama such as Low Winter Sun, in television’s Titanic or in theatre such as Gagarin Way.

Since joining a local drama group aged sixteen and playing Jesus in Godspell, Brian as managed to combine delicious menace with comedy, as evidenced in his iconic Irn Bru appearance, in which he played a pathologically disturbed cuckoo.

McCardie isn’t an actor who takes himself too seriously, and can certainly laugh about some of the less impressive work he has appeared in, such as Speed 2, with Sandra Bullock.

He can also laugh at the vagaries of acting fortune. Recently Brian was in Iceland, filming the second series of Fortitude for Sky Atlantic, alongside star names such as Denis Quaid, Sofie Gråbøl and Richard Dormer.

“Everything was meticulously organised by the producers, all the cars and trucks set to take us to the film location. But we came out one morning all the trucks, cars, were gone. Vanished. I couldn’t believe it.

“Then it was explained to me the trucks hadn’t gone at all. There has been a fifteen feet snow fall and they were buried underneath. It took three days to dig them out and get to work again.”

All that was dealt with. Right now, he’s focused on becoming James Connolly again, but this time he’ll be all alone on stage.

“I’m worried about remembering all the lines,” he admits, not using those exact words.

“There’s such a lot to get across, the story, the character detail, remembering he was slightly bowl-legged, probably because he suffered from rickets.”

It’s clearly a labour of love, but was there anything he didn’t like about the man who made the ultimate sacrifice for socialism?

“Yes, he was a Hibs supporter,” says the actor, laughing.

“And I’ve had to grow a James Connolly moustache, which I’ve come to realise is absolutely repellent to women.”

• Connolly, The Citizens’ Theatre, until tomorrow.