Clare, 17, is often reminded by her family that her grandfather would turn in his grave if he knew she was going out with a "Fenian"; her mother lives in dread that they will marry one day and have the ceremony in a Catholic church. Niall, 19, grew up on the Falls Road in Belfast, one of the most notoriously republican areas, where a Protestant would never have dared to venture before the ceasefire.
They met at a summer camp for young people of all faiths last year, one of a growing number of cross-community projects working in Northern Ireland, both publicly and underground, among people who often live in complete isolation from one another. After the camp they began to attend a group that meets every Wednesday night at the civic centre beside two staunchly Catholic estates, Poleglass and Twinbrook. It was set up by Youth Initiatives, led by two Americans, who were invited there by the local Catholic priest to work with the community.
Niall and Clare gradually became best friends, and their social lives started to revolve around weekly meetings at the centre. They also began going round to each other's houses. Clare was nervous of the Falls Road at first, and her mother often teases Niall, asking him last week if he was going to join in the Orange marches, but they get on with both families. "We were really good friends and got very close before we actually started going out, although I think we both knew it was going to happen," Clare says. "There was a lot of flirting in between, we flirted for about three months, but I think I was ready to go out before he was."
"We're just like any other couple," Niall says, "and we never really thought about religion. Every time we saw each other was at the group, and nobody cares less what religion you are there."
For older generations, prejudice and bitterness may always run too deep. But the ceasefire gave many young people a chance to mix freely for the first time. They go to the same dance clubs, meet on each other's once-forbidden territory and have found normal common interests. Clare says: "When the ceasefire ended my mum said, 'you can't go to his house', because she didn't want me going in a Catholic area. It was like she thinks I've got Protestant written all over my car, and they're going to blow it up. But the ceasefire gave us a real chance to cross barriers we had been brought up to be scared of."
Most children grow up knowing only the differences, the clues that easily identify someone as a "prod" or a "taig": names are the clearest indicator; where someone lives in the roughly east-west divide in Belfast; the football team they support, Celtic or Rangers; even how they pronounce the letter h ("haich" for a Catholic and "aich" for a Protestant), and, of course, whether they go marching on 12 July. The price of crossing the divide has been perilously high for some of the religious and community leaders who have led initiatives. A Protestant minister who crossed the road 10 years ago to offer Christmas greetings to a Catholic family as part of an effort to bring people together was driven out of town; others have been ostracised since, or been targets of violence.
But the the efforts have continued among groups, churches and individuals in the belief that every friendship between the two sides is the only way to build peace. Clare says: "We've really started listening to each other, and we've got to the point where we can talk to each other about the Troubles and our differences.
"I didn't know much about nationalist politics until we became friends. At least it gives you a chance to think, maybe they're both equally wrong. With each generation it's getting better. My parents are slightly better than my grandfather - although they'd still prefer it if I wasn't seeing a Catholic - and we'll be better than them."
Poleglass and Twinbrook estates house around 16,000 Catholics. The area has nearly 80 per cent unemployment and the monotonous white houses and boarded-up flats spread out endlessly into the horizon, broken only by the ominous IRA graffiti on dull walls: Free the PoWs, Disband the RUC, Royal Orange Constabulary.
There is an air of hopelessness on the silent streets, broken only by the laughter coming from the civic centre. Jamie Treadwell, the director of Youth Initiatives and a Protestant, says: "When the prospect is unemployment, that means no future so the present is not worth very much either. Violence doesn't mean very much, because people feel they're losers anyway.
"At the lads' meeting this week, the first since the parade, they were saying that this conflict was in their blood, and they could imagine being drawn into the IRA, and that without the group they would have no means of venting their anger and frustration."
Inside the centre, in a plain white room devoid of any cultural references apart from a painting that has the words Peace for Belfast above it, the laughter has subsided for prayers. Individuals shout out their concerns and hopes spontaneously: that the politicians will be responsible for what they say; that the milk van driver, badly burnt in the violence, will recover; that the weather was beautiful and they should all be grateful for it.
Even in the most troubled times the group has continued to work across the community. After the Shankhill bomb in October 1993, when bitterness brimmed over in Belfast, the group wrote and produced a play to perform in loyalist territory on the other side of the city, to young Protestants. It was called Belfast Born and told the story of two twins, one Catholic, the other Protestant, who were separated at birth. They fell into bitter rivalry throughout every stage of their lives and only discovered as old men that they were the same all along.
Young people at Poleglass have remained optimistic, but even for the generation just above them, men and women in their mid-twenties, the mood is more sombre and much sense of idealism has gone. Seamus and Sadie, both 27, met at Queen's University, one of the most mixed institutions in Belfast. He is from a Catholic family, and she from a Protestant background. When the ceasefire ended, many of their fears returned as a part of normal everyday life. "It was such a dramatic end," says Seamus. "I was watching a play about the ceasefire in Armagh on the night of the Canary Wharf bombing, and I think we were the only people who knew it had happened. It was strange to sit though such a positive play knowing it was all over."
For Sadie, one of the most disturbing fears is that Seamus will be targeted, particularly in the atmosphere of heightened tension and the return to bitter recriminations on each side. "Before the ceasefire you'd hear things on the news, three men killed, and you'd be waiting to hear the professions, then you'd find you were glad when someone else was dead, because it wasn't Seamus. I'm probably more worried about him than he is about me now, because they're more likely to get him. A Catholic man his age is a target for getting shot."
Neither is practising the religions they grew up with, and both say that they will not marry. The pressures on their families would be too much, and because they have no belief in the faiths that have divided Northern Ireland in the first place, they see no point. Seamus says: "We're just not interested in all of that. It'd be all that stuff about what religion would we get married in. It's only a problem if you're practising, and we're not and never will be."
They live a largely anonymous existence in the south of Belfast, locking the doors carefully each night, mixing with the Queen's University community. Sadie says they may move to England or to the south if the Troubles continue.
At the Dairy Farm civic centre in Poleglass, the discussion moves on to "relationships", amid some sniggers from two boys on the back row. One of the religious brothers from the lay order that represents both Protestants and Catholics in the group, breaks through the chatter and asks what images the word conjures up. "Sex," shouts one teenager; "Girls," bellows another; "Boys," returns a third. The brother appeals for calm.
The atmosphere changes dramatically as he praises the forgiveness of the father of a taxi driver killed during the violence last week. "The man went on TV and said he, his wife and family forgave the people that did that. What I want to say to you is that if you start by forgiving people in small things, you move up to the big things."
For their part, Clare and Niall believe that their friendship may help contribute to the "big things". "You have start somewhere, and if two people can do it, others can. The barriers start to come down for more and more people," says Niall.
Their future is, they say, as fraught as they choose to make it. Mixed couples in Belfast are still targets, and the violence that erupted last week over the Drumcree parade reopened old wounds on all sides. They hope to go to Queen's University, where Clare will study English and Niall medicine. They shyly suggest that they have talked about marriage one day, and no, they cannot agree on which church, but they do not believe it would be a real problem.
The future of their homeland, despite their optimism, remains less clear. Clare says: "I've got to look at myself and say I am the hope for the future, and I have to look at Niall and the people around me and say things can change. I've got to believe it. I've always said there is something special about this place, I love it, and we've got to make a go of it."
The names of Niall, Clare, Seamus and Sadie have been changed at their request.