Now all that is behind Walsh. He is in the park with the children in an effort to make up for lost time. Like other republicans and loyalists who have served long sentences during the Troubles, he became a grandfather without ever really being a father. Soon, others like him will be released to recommence domestic lives which were dramatically abandoned. As a result of the Good Friday Agreement, a handful have already been freed. By Christmas, hundreds will be out. Within two years, the political wings of Northern Ireland's prisons should be empty.
In the park, the children kick fallen leaves, play on the swings and spin on the roundabout. They remind Walsh of what he left behind. When he went to England in 1973, he assured Mary, his heavily pregnant wife, that he would be home in time for the birth of their second child. But Roisin was born in his absence. Indeed, he missed her first Communion, her confirmation, all her schooling and her entire upbringing. He did not return home from prison for 21 years, until just before Roisin's marriage. While other parents prize memories of their children growing up, he has few. He treasures a yellowed telegram he received in prison. "Baby fine," it says. The children in the park are Roisin's.
These days, when you meet Roy Walsh, there is not much of a folk hero about him. Like most ex-prisoners, he dresses young - new trainers and jeans - but at the age of 49 he looks fairly shattered. A little bewildered by life, he also has heart problems. In his car, he drives fast, calming himself with frequent cigarettes, singing along to a worn out cassette playing "Kevin Barry", "Four Green Fields" and other republican songs. At home, he finds it hard to sit still. He rushes around the living room while we talk, fixing a squeaking door hinge with oil and phoning someone about the prisoners' campaign for which he now works. It is as though, says his wife, he is trying to cram the 21 years he lost into every week. He looks like a man fighting off depression or an awful reckoning of loss which might come with stillness.
Walsh has come back into a family tormented by the consequences of his actions; the years of poverty, estrangement and anguish. Their children, Patrick and Roisin, have had to come to terms with a father whose actions put them second to "the Cause". For most of the 21 years he spent in prison, his wife and children lived in miserable circumstances. Home was a small flat in west Belfast's infamous Divis flats, a tower block riddled with hoods and joy riders, which became a by-word for Catholic deprivation. Mary Walsh, a tiny, jolly woman, blessed with unflagging optimism, was the victim of several muggings.
Mary is delighted with her new home, a neat, modern council house off the Springfield Road in west Belfast. The only reminder of the days of guns and bombs is a photograph of those who led the 1916 Easter Rising, signed by dozens of republican prisoners. But the past cannot be tidied away like so many old photographs. Four years after her father's release, Roisin, now 25, is still not comfortable kissing and cuddling her father. "They never had that time to bond when she was young," says Mary. Their elder son, 26-year-old Patrick, who was 15 months old when his father left, is more relaxed with him. However, even he says he was shocked when, for the first time in his life, there was another man living in the house.
The children had become used to seeing this stranger perhaps twice a year for an hour or two after long journeys to different prisons in England. In that time, they were never left alone with their father. There was often a glass partition separating them from him. What do you say to a father who has come to live with you after 21 years away?
Many other families must be contemplating such a question. Walsh was outside the Maze earlier this month to greet the first of those released under the Good Friday Agreement. "There was one of them, in particular, who was looking around," he recalls. "You could see how disorientated this fellow was, not knowing which way to go." Like Walsh, who got out in 1994, these men were feted at huge parties. But Walsh also knows that the morning after, once the debris of celebration has been cleared away, they must face up to the mess of the lives they left behind.
Seven out of 10 of those who went into prison married will return to homes where they are no longer wanted or which have been abandoned by their wives. So says Robert McClenaghan, another ex-IRA man who served 12 years of a 20-year sentence for carrying explosives, and now runs a group for ex-prisoners who build new homes for themselves. Long-term prisoners lucky enough to find a woman waiting for them may have to accept that their wives have borne children by other men.
There is much debate about what is to be done for such men. "We have to ask ourselves," says McClenaghan, "whether we are going to leave them on the margins of society, as outcasts. If we do not provide them with security and support, they will drift. You will have living time-bombs walking around. You could have another Dunblane. They need help getting their relationships together. Everyone has changed. The women have become stronger; they have been forced to deal with the finances and bringing up the children on their own. There is anger that easily spills over. I get men crying down the phone to me at two in the morning. They don't know how to cope."
The freed are fragile. I talk to the wife of a man recently released: the family must not be identified, she says; they are trying to set up a new life. Their sons are in new schools where no one knows their background. Her husband, she says, is finding the transition hard after being in jail for nearly seven years. "He says that when he was in prison he had only himself to think of all day. Now he is preoccupied with the boys, taking them to school, to football matches, to see friends. He's exhausted. And then, I say, he has to fit a job in as well. That's what I've been doing all these years."
Of the 10-strong gang which bombed the Old Bailey, four were married. Only Roy and Mary Walsh are still together. Just.
"When he first came out," says Mary, "I used to wake up in the morning and say to myself: `Who is this man beside me?' We were just like two strangers. There were things I could tell someone else but not Roy, and the same with him. A lot of times, I wondered whether it was worth holding this marriage together? When he first came out on parole for weekends, he would be out on a Friday morning and he would be drinking, so I wouldn't see him until Sunday or Monday."
It was a pattern which carried on for 18 months, until well after he was completely free. "We weren't used to someone coming into the house with drink on them. Roisin used to say to me, `Why do you put up with it?' And if it hadn't stopped, if it had taken two years instead of 18 months, I might not have.
"There was that selfish streak in him when he came out. He had done all that time, so he felt he had needs. But what about our needs, me and the children? He felt he had been in prison so he was the victim. But we may as well have been prisoners all those years.
"Money meant nothing to him. But it meant everything to me because it was how I kept this home going. Roy thought he needed it to go out and have a good time. And do you know one of the hardest things to accept? It took Roy a long time to say `I love you' - even to the children and me. That was hard.
"But when you know someone is a good person and there is something worth holding on to, you fight. In the end, Roy needed us more than we needed Roy. Without us, I don't think he would have survived."
Walsh nods. "I went a wee bit wild. I think I drank to forget the hard times in prison, the depressing times when my mother died and when Mary's mother died." He spent nearly five years in solitary confinement and was moved 71 times. "When I first got out, if there was a party on, I'd be at it. That went on for 18 months. Then one day I decided I'd had enough of that. It has been very strange, being out. I was brought up in Divis and the Lower Falls. By the time I came out it had all been knocked down. For a while I couldn't find my way about."
In recognition of the problem, Walsh, McClenaghan and several other republican ex-prisoners have gone on a fact-finding mission to South Africa. They will seek advice from the ANC on how it has rehabilitated people who have few skills beyond using a gun and making explosives. The trip to the airport is a bizarre, macabre journey as these ex-IRA men reminisce about disastrous missions, the time one of them ran out of petrol, the alarm clocks that didn't work properly. A conflict which is still so recent suddenly sounds like ancient history, the stuff of banter and misty-eyed remembrance. But these men know that the battles of peace time are far from over.
When they return, they will need to be ready for men such as Paddy McLaughlin, due out soon. McLaughlin has served 11 years of a 20-year sentence for conspiracy to cause explosions. He has never had a proper job. This is his third stretch inside during the Troubles; he has six children. Like Walsh, he is another IRA grandfather. Three of his daughters, the eldest of whom was 12 when he was most recently jailed, now have families of their own. For four years after his last conviction, his wife Margaret travelled from Belfast, often with all the children, to visit him in English jails. "I idolised him," she says. "I just told the children their daddy was in jail for something he didn't do. He only told them a couple of years ago that it was political."
However, an already turbulent relationship foundered under the strain. "I had always hoped that he would change," she says. "I wanted him to look after me and the kids." He divorced her after she began a new relationship and became pregnant with Bridget.
Margaret recalls: "I was so happy. Bridget's father swore that he wasn't involved in anything. Then he went out one day and did not return. He was also arrested with a bomb. I had never suspected a thing. I nearly had a breakdown. He got 20 years as well. I visited him for a year and then I just got fed up and got on with my life. It had a terribly bad effect on the kids."
Both men are now in the Maze prison and are due out soon. Each has married other women in the last year. Margaret remains a lone parent. Bridget, now 7, cries whenever her mother leaves her. "I feel such a fool. They really let me down," says Margaret.
Margaret shows me pictures of Paddy McLaughlin in the Maze holding his children. "He looks like he's been on a holiday," she says. "I know what I'm going to do when he gets out," she says. "I'll tell him, `Here are your children. You take them. I need some time for myself'."