James Nesbitt playing Ivan Cooper in Bloody Sunday
Ivan Cooper is not a name on the lips of many people.
The former Stormont MP has spent almost 20 years in happy and relative obscurity as an insolvency consultant in Londonderry.
Mr Cooper was one of the major figures of the 1960s civil rights movement and a founder member of the nationalist SDLP - a political stance that led many of his own Protestant community to brand him a traitor.
Yet at the height of his political activity, he had the largest support of any nationalist MP elected to Stormont before the introduction of Direct Rule. Not bad for a working class kid who grew up playing football in Derry's Bogside.
In Paul Greengrass's film, James Nesbitt plays the young Ivan Cooper who witnesses the chaos, death and subsequent stratospheric rise of the Provisional IRA in response.
"I've seen the film six times now," says Mr Cooper, now 58. "And my first thoughts were that it was an emotional experience. I'm able to say with confidence that it was made with great integrity."
Most of all, he believes that the film will play a great part in healing the wounds and helping Derry as a city to move on, something he detected at the first screening with the families.
"The Saville Inquiry has started a process and the families really need his judicial declaration of innocence.
"But I also think that the film has been very helpful - it's going to help make it possible to put Bloody Sunday behind us much faster than otherwise."
Civil rights ethos
Mr Cooper's rise to prominence was helped because he turned his back on the Protestant/Unionist politics of his own community.
He believed that the working classes of both communities could put sectarianism behind them through human rights and reform.
"It's difficult for people to appreciate the ethos of the non-violence movement at the time," says Mr Cooper. "It was almost like a religion which you were indoctrinated into.
"But internment was the big issue that would ultimately do more harm than good.
"Before Bloody Sunday, I believe there were no more than 30 to 40 IRA volunteers in Derry. They had a very small base, small amounts of hardware and, most importantly, very little support.
"The support was with John Hume and Ivan Cooper. We were still reasonably integrated in the city.
"The IRA's campaign of violence that followed in the wake of Bloody Sunday [and internment] changed all that."
Idealism and naivety
Mr Cooper remains a self-confessed idealist who came to politics because he believed in "the notion that Catholic and Protestant working classes could be united".
"It would have been possible," he says, adding that the IRA's violence did far more to drive a wedge between the two communities than anything else in Northern Ireland.
"If anything, their campaign has put the goal of a united Ireland further away. The violence delayed the power-sharing that we now have and polarised communities.
"So what have the republicans got to show for it? Four members of Parliament in Westminster. Was that what republicanism was all about?"
Republican conversions?
One of those MPs, Martin McGuinness, is the most awaited witness at the Saville Inquiry into the events of Bloody Sunday.
Mr Cooper believes that the education minister who recently admitted he was an IRA commander in 1972 has turned from violence.
"McGuinness has realised that violence does not work," he says. "He now knows that his dream of a united Ireland through the bomb and the bullet is not possible. We have to welcome that."
Drifting away
Mr Cooper, by his own admission, slowly drifted away from politics as it was squeezed more and more by the violence.
In 1983 he stood aside in Derry to allow John Hume, by then party leader, to fight and win the new Foyle constituency.
The two men remain close friends but Mr Cooper admits that he can't get politics out of his blood.
"I miss it very much. If you have been in politics, it's something that stays with you."
So from his position on the sidelines, where does he see politics heading?
"I think that Northern Ireland is a lot more mature place politically than it's given credit for. I have friends and business clients who know where I come from politically and what I did. They may not share my views but we can sit down and debate it.
"I've also been encouraged by the general Protestant reaction to the Bloody Sunday films [a second film by Jimmy McGovern was produced for Channel 4].
"I think it has been amazingly muted and perhaps that's because everyone knows that something terrible was done on that day.
"For years Catholic schools have done project work on Bloody Sunday. Now I'm having invitations from Protestant schools to go and talk about what happened.
"I think that's a very good sign. I have faith in the young people of Northern Ireland."