Like most people of my postwar generation in Britain, I started thinking about Northern Ireland only when the shooting started. I had no family connection with Ireland. We never learned about Ireland at school. I didn’t read a book about Ireland until I was at university. And I never went to Ireland, north or south, until I was in my 20s.

My guess is that most of this was pretty typical of its era. As a boy, I knew Northern Ireland was part of the United Kingdom. But what else? George Best was about as far as it went. The Irish seemed to be like us but were not talked about with affection, the way Australians were. Later I learned why that was. But the fact that Northern Ireland was in effect a one-party state, in which half of the population was routinely discriminated against, was simply not on our radar.

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All that changed with the start of the Troubles. For the next 30 years, it was impossible to be British and not know about Northern Ireland, even if you didn’t want to. I first heard Ian Paisley speak in 1967. In 1973, I heard the car bombs explode outside the Old Bailey. In 1996, an IRA bomb wrecked part of the Guardian’s printworks in London’s Docklands. But then, in 1998, all that stopped.

The Good Friday agreement, which was signed 20 years ago next week, did not solve all the problems in Northern Ireland. Much of it was based on an agreement to disagree – including even about what to call the deal itself. But it was a historic and massively beneficial trade-off for the people of the north. It brought peace. It brought fairness. Above all, it brought a new kind of ordinary life.

And with the coming of ordinary life, there slowly grew up once more in Britain a kind of neglect of Ireland. Eventually, after a few false starts, Northern Ireland began to govern itself. After a while, British politicians did not need to get involved so much. Understandably, Gordon Brown spent less time thinking about Ireland than Tony Blair and John Major had done; David Cameron and Theresa May spent even less. Political leaders in Britain did not want to get sucked in. Even in the Irish Republic, there was a certain distance and a long slow sigh of relief.

In one sense, the return of neglect represents a continuity. English, later British, indifference to Ireland has deep roots. Many would use much stronger language, especially about the era when English Protestantism was at its most militantly anti-Catholic. My generation of English people wasn’t the first to be brought up in ignorance about Ireland. But that habit of ignorance was an institutionalised one. English schools have never taught their pupils much about the history, literature or culture of Scotland or Wales, never mind Ireland, and they don’t do so now.

In another way, though, the lack of interest in Ireland makes benign sense. There is far more cooperation and mutual respect than there was before. Much of this has to do with being in the European Union for so long. But it is also because the world is much more connected and liberal than it was. British and Irish people inhabit shared cultures without thinking or fretting about it. Most of us should be fine with that.

Brexit clearly threatens this. The harder the border between north and south, the more reckless the UK’s decision to leave the EU will be judged. But even a hard border would be unlikely to herald the return of the bomber and the gunman, or the redeployment of thousands of troops, or the reimposition of a discriminatory sectarian state in the north. The collective failure in Northern Ireland can’t be blamed just on Brexit.

It is a fact that the 20th anniversary of the Good Friday agreement is not getting anything like the attention it merits in Britain. This neglect should cause great concern. This was, after all, a historic deal for both islands. It reflected extraordinarily well on all those who crafted it. It established, you might almost say, a new sort of truth about the importance of compromise in politics. Yet the silence across much of the UK media on the subject is deafening – and dishonourable.

Brexit is a symptom of British unease, not just a spanner in the works

Contrast this with Ireland, and with Northern Ireland in particular. There will be big political and cultural events in Dublin and Belfast next week, with Bill Clinton and George Mitchell still expected to join politicians from both sides of the Northern Ireland divide – David Trimble and Gerry Adams, Peter Robinson and Seamus Mallon among them. Here in Britain? As far as one can see, it has fallen to the Irish embassy in London to lay on the nearest thing to a party – a cultural evening at the Barbican.

It is hard to say precisely why the British eye has been taken off the peace process. Brexit is part of it, but Brexit is also a symptom of British unease, not just a spanner in the works. Important too is the fact that we have moved into the second generation now. Clinton, Blair, Bertie Ahern, Adams, Trimble and Paisley and the rest have all left the stage. Their successors were not direct participants – not even the Democratic Unionist leader, Arlene Foster, though her father was shot by the IRA and her school bus was bombed.

The Good Friday agreement stopped the violence. But it did not stop the sectarianism. There has been no Northern Ireland assembly or power-sharing executive now for over a year. The last efforts to relaunch them ended in confusion and mutual obduracy in February. Even optimists think there will be no serious attempt at movement until the autumn.

This might not have happened if the new generation of politicians and officials in London, Dublin and Belfast had been under greater domestic and international pressure to move forward. The ostensible question dividing the two sides in Belfast – recognition of the Irish language – is neither fundamental nor insoluble. Instead it has become a convenient proxy.

May has been caught out by the inexperience she shares with her generation. In particular, she has consistently misjudged the DUP. She gave them a Westminster pact last summer when she didn’t need to do so, misread their readiness to endorse the first phase of the Brexit deal in December, and rushed prematurely to Belfast to sign off on a resumed power-sharing deal that Foster could not deliver, possibly because her party’s Westminster MPs pulled the rug from under her feet.

Making a success of the agreement of two decades ago requires knowledge, attitude and will on all sides. Britain displays none of these things with the requisite consistency any more. The result is a huge missed opportunity. The people of these islands have rarely been more convergent or neighbourly than they have been over the past 20 years. But it is hard to believe that the same will be said after the next 20.

• Martin Kettle is a Guardian columnist