rguments about difficult parts of British history have been a feature of 2020. But it is striking that something as important in its continuing consequences as the partition of Ireland, which took place 100 years ago this month, has been so widely neglected. There has been plenty of reflection on partition in Ireland itself, but there has not been much in Britain, which created the divide in the Government of Ireland Act 1920. The closure of the British mind regarding Ireland is not new. But it remains glaringly topical in the light of Brexit. Irish partition still underpins one of the most charged dilemmas in Britain’s process of European disengagement. As recently as Monday, Michael Gove and the European commission vice-president, Maros Šefčovič, crafted a British climbdown over the future international regulatory status of Northern Ireland, one of the territories that partition created in 1920. Optimists have seized on the new Northern Ireland agreement as a sign that London is finally in the business of Brexit deal-making. Let’s wait and see about that. Economics and politics pull many Conservatives in different directions on Brexit, including Boris Johnson. But Johnson has always put the party politics of the break with Europe ahead of the national economics. That is why scepticism about the eventual outcome remains in order for now. A more reliable truth is that the new Northern Ireland agreement was inescapable, regardless of whether it becomes part of a wider EU trade deal. Northern Ireland’s interconnections with the Irish Republic – economic, political and cultural – necessitated it. The UK sovereignty dogma that dominates every other aspect of hardline Brexit ideology had to be compromised if peace was to be maintained in Ireland. Joe Biden’s election may have concentrated minds here. But the reality existed all along. The government climbdown over the law-breaking clauses in the internal market bill has been brewing for weeks. The climbdown was always likelier once Dominic Cummings had lost his grip over Brexit policy, when he resigned last month. Cummings did not care about Northern Ireland, international law or reputational damage. But he did care about delivering a full-sovereignty Brexit. It was what he was originally in Downing Street to deliver. The controversial parts of the internal market bill were pure Cummings. He would have been maliciously relaxed about reneging on parts of the withdrawal agreement that got in the way of a complete break with Europe. Cummings was still riding high when those treaty-breaking clauses were published in early September. But his provocation strategy got more difficult as the clock ticked down towards Britain’s December departure, and after Biden ousted Donald Trump. This strengthened Johnson and Gove in their readiness not to allow Northern Ireland to derail their Brexit in the same way it derailed that of Theresa May. When you stand back and reflect, all this is in part a direct consequence of partition a century ago. The Northern Ireland Brexit protocol would not have been relevant if both the south and the north had each remained within the UK, as the framers of the 1920 act vainly hoped. Instead partition became an international border that has endured for 100 years. And it has created – and is still creating – issues that have to be dealt with by new generations throughout these islands. This is not to denounce partition as a denial of nationhood in the way that nationalists often do. My point is less emotionally charged than that. It is that events that appear to be a solution to one apparently intractable political problem, which partition of Ireland was certainly intended to be, end up creating a set of different political problems down the track. This will surely be true of Brexit too. This was unquestionably true of partition. The new problems exploded into life as soon as the 1920 act received royal assent. Most importantly of all, a lot of people died because of it, on both sides of the border and in Britain over the ensuing 80 years. But partition shaped constitutional politics too, east and west as well as south and north, for even longer. Nearly a century on, May’s pact with the DUP from 2017 until 2019 gave that party a stranglehold over her Brexit policy that produced the backstop that ultimately brought her down. Partition has been mitigated several times over the years. When Britain and Ireland joined Europe in 1973, regulatory regimes in both parts of Ireland began to move closer. The Belfast agreement of 1998 strengthened and formalised the process. This could be another significant lesson for the evolution of Brexit, though hopefully it need not take so many decades for the mitigation to begin. Settling Brexit once and for all may have been the Conservative party’s wishful goal in the election that took place 12 months ago. But it has simply not happened, in spite of Britain’s departure from the EU. Nor will it happen. Like partition, the issues that getting Brexit done was supposed to resolve will still be live when those who voted in 2016 are long dead. Brexit is already creating these new iterations. They include Britain’s interactions with Europe. These are not going to disappear or stand still. Nor are Northern Ireland’s interactions with the Irish Republic, where the same is true. Most urgently of all, the new issues now also include whether the internal cohesion of the UK itself can survive the departure from Europe. Hopefully no one will die as a direct result of Brexit, in the way so many died after partition. But Brexit is not the end of the line. It is merely a stop along the way. Get Brexit done? Get real. Brexit will never be “done”. Not even by 2120. • Martin Kettle is a Guardian columnist