All smiles: (from left) then Taoiseach Bertie Ahern, former US Senator George Mitchell and then Prime Minister Tony Blair after the signing of the agreement at Stormont

Still divided: the largest peace wall in Belfast at Cupar Way, which separates the Catholic Falls Road from the Protestant Shankill area

At the Beechhill fishery near Belfast, anglers relax next to the pond and reel in their catch on a showery spring afternoon. The Northern Ireland Cross Community Angling Club attracts hundreds of enthusiasts from housing estates and flats across the city and beyond.

One of the volunteer organisers, Scott Lonsdale, says: "The mood here is chilled and relaxed. When people are fishing, they are escaping from their lives in the city - and we do not care who they are."

There is no need for peace walls in this soothing enclave away from the hurly-burly. As the website of the cross-community club puts it, there are no barriers of creed, nationality, language or age around here. According to Scott, fishing is something to be enjoyed by everyone who turns up.

Twenty years after the Good Friday Agreement was signed, fishing is one area where any lingering community tensions in Belfast's working class areas can be ignored and literally cast aside. As one angler tells me: "Fish know no borders."

But, two decades after the agreement was brokered at Stormont, with the world's Press there to witness the hand of history on then-Prime Minister Tony Blair's shoulder, the Northern Ireland which it produced is the proverbial curate's egg: its critics would say it only works well in parts.

It has not created a utopia, but the signatories can at least console themselves at the commemorations that the violence has not returned.

Jonny Byrne, lecturer in criminology at Ulster University, has studied closely the barriers between some communities across Northern Ireland. "What we see is a twin-track peace process," he says. "For half the population, it has been fantastic and their lives have changed fundamentally for the better."

The centre of Belfast - with Titanic Quarter, Victoria Square and St George's Market - has been revamped and is, in parts, unrecognisable. But not everybody has seen the benefits of a Troubles-free city.

"There are communities across the north where little has changed - apart from the absence of violence," Mr Byrne adds.

In the middle-class areas of south Belfast, communities mix freely, as they always did to a certain extent during the Troubles. More than half of the population believe community relations have improved, the Northern Ireland Good Relations Indicators survey suggested recently.

The survey found that 52% of adults and 59% of young people believed relationships between Catholics and Protestants are better than five years ago.

But that still leaves a significant section of the population who do not believe relations have improved significantly.

When he brokered the Good Friday Agreement 20 years ago, US Senator George Mitchell spoke of his vision for the future of Northern Ireland. "I have a new dream; to return to Northern Ireland in a few years and sit in the visitors' gallery in the northern Assembly," he said.

"There we will watch and listen as the members debate the ordinary issues of life in a democratic society. There will be no talk of war, for the war will have long been over. There will be no talk of peace, for peace will be taken for granted.

"On that day, the day on which peace is taken for granted in Northern Ireland, I will be fulfilled and the people of goodwill everywhere will rejoice."

The guns may be silent and consigned to arms dumps, but there is still a sense that Northern Ireland has not escaped from the legacy of the conflict.

It is a deeply embedded part of the culture that still haunts the society.

"We have not yet found a new language for the post-conflict period," says Jonny Byrne. "We are still talking as if the Troubles were still on, about the legacy of the conflict, security, peace walls and paramilitaries."

George Mitchell's hopes that Northern Ireland politicians could escape issues of war and peace in their Assembly have been dashed.

The Troubles are constantly raised in the back-and-forth debates between the DUP and Sinn Fein.

And most disappointingly of all for Senator Mitchell, the Assembly itself is not up and running, discussing and working through the humdrum details of everyday life. But at least, some form of peace has somehow held together through it all.

"You could say there are probably at least 1,000 people who are alive today because of the Good Friday Agreement and the absence of large-scale violence," says Peter Sheridan, chief executive of Co-operation Ireland and a former PSNI police officer.

"We are not spending our time walking behind coffins every day and seeing bombs exploding on the street every day, and people have tended to forget that."

Sheridan says that one of the most positive legacies of the Good Friday Agreement is the invisibility of the border.

The former policeman recalls how different the border was at the time of the agreement.

By the time the deal had been signed, the customs posts had already gone, but there was still a heavy security presence.

"People forget that, along 10 miles of the border in south Armagh, there were 12 Army watchtowers, four helicopter landing sites, six permanent checkpoints, four police stations and many roads sealed off."

Under the Good Friday Agreement, unionists could still preserve their British identity in the UK, while nationalists could assert their Irishness, feeling a sense of unity across a border that didn't seem to exist.

According to Sheridan, there was also a growing tendency of people to see their nationality as Northern Irish.

The problem now is that Brexit and the question marks over the border have created a new mood of political and economic uncertainty amid fears that a physical frontier will return.

The absence of large-scale violence may be something to celebrate 20 years on.

However, Sheridan believes that genuine reconciliation needs to go a lot further in Northern Ireland.

"Most of us underestimated how long it would take," he says. "Peace is not just about an absence of violence. It is about learning to live together as citizens."

When it comes to genuine integration, the picture in Northern Ireland is a decidedly mixed bag.

Michael Wardlow, of the Equality Commission, says workplaces have changed dramatically over the past 20 years and are much more mixed than they used to be.

However, the number of children who are educated together in integrated schools remains stubbornly low.

When he was First Minister, Peter Robinson described Northern Ireland's education system as a "benign form of apartheid which is fundamentally damaging to our society".

Out of 340,000 children currently going through school in Northern Ireland, just 23,000 are in integrated schools.

"There is a big demand for integrated schooling among parents, but it is not being incentivised enough," says Mr Wardlow.

Research by academics at Queen's University showed that children who attended integrated schools were more likely to reject traditional identities and allegiances than those who had attended a segregated school.

While only 7% of children go to integrated schools, there is a new emphasis on "shared education", where students from different schools come together.

While fully integrated schooling has been slow to materialise, schools are being encouraged to share classes, facilities, teachers and even buildings.

In one of the most ambitious projects, up to 4,000 pupils from six schools in Omagh will be educated on a single campus at Strule, the site of the former Lisanelly Army base.

While the overall research figures show a softening in attitudes between communities, there are some areas across Northern Ireland that continue to have physical and psychological barriers between them.

There is no more potent symbol of this division than the 'peace walls' that divide communities in Belfast, Londonderry and some towns across Northern Ireland.

The Cupar Way wall is among the most famous, dividing the loyalist Shankill area from the nationalist Falls Road.

Built as a "temporary measure" almost half a century ago, it is now almost double the height of the Berlin Wall.

Adrian Johnston, chairman of the International Fund for Ireland, says: "There are now more peace walls in Northern Ireland than there were when the Good Friday Agreement was signed."

Mr Johnston said only a minority of people in the areas near the barriers wanted them taken away immediately, but the vast majority wanted them removed within the lifetime of their children or grandchildren.

It is no coincidence that every area where there are peace walls are among the most socially deprived enclaves across Northern Ireland and these were the areas that were most heavily scarred by the Troubles.

According to the International Fund for Ireland, nearly 70% of Trouble-related murders took place within 500 yards of the peace walls.

"It did not help of course that these interface areas were among the most heavily hit by unemployment during the economic crisis," says Peter Sheridan.

Many who want the peace walls preserved say they do so for the sake of security, but Jonny Byrne says they are also seen as a way to demarcate territory. "They are now perhaps less about security than protecting identity," he says.

He adds the experience of the Troubles in Northern Ireland was highly variable and some people were hardly touched by it all.

"Northern Ireland is a paradox, where you can live cheek-by-jowl, and one community experienced almost nothing during the Troubles, and another experienced the most horrific instances of violence," he says.

Twenty years after the agreement, Northern Ireland has reached a point of political stalemate - and Brexit has worsened tensions.

"What we need now is maturity, leadership and a willingness to take risks," says Mr Byrne.

Those qualities were not lacking among the motley bunch of politicians who came together to sign the Good Friday Agreement in 1998.

It remains to be seen if they can be found among the present generation of leaders, who have shown a reluctance to put aside divisions and govern together.

Belfast Telegraph