A friend – a Northern Ireland Protestant who now lives in England – has just returned from a family wedding in Belfast. He found it eye-opening. The bride and groom are in what used to be called a "mixed marriage", meaning one is Protestant, the other Roman Catholic. Several decades ago, that used to be unusual given the sectarian divisions in Northern Ireland, but it is much less unusual now. My friend told me that what was remarkable was to see the generational differences. Wedding guests over the age of 50 did not oppose the marriage, but some seemed to feel slightly uneasy, as my friend put it, that "people from different communities were getting married". The younger wedding guests didn’t see anything odd about two people who love each other, getting married. They have different religious backgrounds? So what? Accurate figures are difficult to obtain but in 2002, research by the University of Ulster showed that Catholic-Protestant couples made up 10 per cent of Northern Ireland's married population – up from 6 per cent in 1989. Northern Ireland has changed significantly since the Good Friday Agreement of 1998 brought (mostly) peace. Another astonishing change is that Sinn Fein is now the largest political party in Parliament at Stormont as a result of <a href="https://www.thenationalnews.com/opinion/comment/2022/05/08/no-northern-ireland-didnt-just-vote-to-break-away-from-the-uk/">this month’s election</a>. The "Shinners", as they are often known, were once the political wing of the paramilitary Irish Republican Army. Their success is a political earthquake because the Stormont Parliament, and Northern Ireland itself, were designed 100 years ago precisely to keep Irish republicans out of power. After what was known as the “Anglo-Irish War” in the 1920s, the British agreed to partition Ireland. The 26 counties of what is now the Irish Republic seceded from the UK. The six counties of Northern Ireland remained. Those six counties were chosen because they were thought to guarantee a Protestant (and unionist) majority. But now Brexit has plunged all this into a new turmoil. Northern Ireland voters chose to reject Brexit in 2016 and stay in the EU. Nevertheless, Boris Johnson’s government made the profoundly damaging decision of imposing a bizarre form of Brexit involving, in essence, moving the Irish border into the Irish Sea, with Northern Ireland treated, in customs terms, as if it were part of the Irish Republic. Mr Johnson agreed that customs checks must take place between Northern Ireland and the rest of the UK. Northern Ireland unionists – mostly Protestants – are furious that their British identity has been undermined. I happened to be in Belfast a few days after Mr Johnson met the then Irish prime minister Leo Varadkar in 2019 and announced this new arrangement. Unionist friends were astonished and appalled. One said Mr Johnson had “thrown 100 years of Ulster unionism into the Irish Sea". The UK Prime Minister then went on to sign the agreement, which sealed the terms under which his country left the EU, and enshrined this new border arrangement legally in <a href="https://www.thenationalnews.com/world/uk-news/2022/05/12/talks-collapse-as-uk-warns-it-must-act-on-northern-ireland-protocol/">"the Northern Ireland Protocol"</a>. Now Mr Johnson is trying to tear up a deal he himself created, reneging on what is an international agreement and – many lawyers insist – in effect breaking the law. Mr Johnson’s legal advisers insist otherwise. Whatever your views on the protocol – and mine always were that it was a catastrophe waiting to happen – the Johnson government has already unsettled Northern Ireland’s uneasy peace and led to the prospect that the newly elected Parliament in Stormont <a href="https://www.thenationalnews.com/world/uk-news/2022/05/13/northern-ireland-assembly-collapses-after-dup-pulls-speaker-vote/">will collapse</a>. The Biden administration and prominent US Congress members are alarmed. So is the Irish government. So is the EU. And despite Mr Johnson telling British voters that he would "get Brexit done", it is clearly not done, since he is trying to renegotiate it. If things were not so serious – possibly putting lives at risk from violence in Northern Ireland – it would almost be comic. The very people who campaigned for Brexit – Mr Johnson, his Conservative party friends and the hardliners of Northern Ireland’s Democratic Unionist Party – now loathe the Brexit that they demanded, constructed, negotiated and agreed. Those of us who for years pointed out the obvious dangers of Brexit can say "we told you so", but that is no consolation. The history of Northern Ireland shows we are never far from a few hotheads prepared to resort to violence after being stirred up by blundering politicians. The past 25 years have seen many good things: peace, stability and economic improvement. Marriages between Catholics and Protestants are much more common. My friends in Northern Ireland want to get on with their lives in peace. However, the incompetence at Westminster over Brexit threatens lives and livelihoods, and the ill-tempered row over the legality of the Northern Ireland Protocol reminds me of the wisdom of the late American poet Carl Sandburg. To paraphrase what he once said: “When the facts are against you, you argue the law. When the law is against you, you argue the facts. When both are against you, you just argue.” Six years after the Brexit vote, Brexit is far from done. And the arguments now mean peace itself may be undone.