IT WAS hailed as historic when Sinn Féin, the party long associated with the Irish Republican Army, beat the largest Unionist party in last week’s elections. Symbolically, at any rate, it overturned more than a century of Unionist dominance in a region that was partitioned in such a way as to guarantee a permanent Protestant majority. But it may prove to be historic for other reasons.

Consider this. The Republican victory did not come about because of a huge increase in the Sinn Féin vote. Although the census later this year is expected to show, for the first time, that Catholics now outnumber Protestants, last week’s poll showed a substantial increase in voters who reject affiliation with either tradition. The non-sectarian centrist Alliance Party won 13.5 per cent of the vote, surging from fifth to third place.

But what was most significant was the fracturing of the Unionist vote, which appeared to have more to do with Brexit than the region’s longstanding tribal divisions. Despite Boris Johnson’s pledging that there would be a border down the Irish Sea “over my dead body”, that is precisely where the border ended up. Unionists, who fear that this will accelerate Irish reunification, are divided on how to respond.

Hardliners, who want the Protocol governing the border to be scrapped totally, voted in significant numbers for the intransigent Traditional Unionist Voice party. Moderates who never wanted to leave the EU switched to the Alliance party. This squeezed the Democratic Unionist Party, reducing its support from 29 per cent of the vote in 2016 to just 21 per cent. The DUP, having backed Mr Johnson in choosing the most extreme form of Brexit possible, have reaped what they had sown.

Yet the continuing fall-out from Brexit is not confined to Northern Ireland. In Scotland, where voting intentions are now governed largely by attitudes to Scottish identity, Brexit — along with a general disdain for the current Conservative government — appears to be hardening support for Scottish independence.

Some detect an impact in England, too. The former Labour Cabinet Minister, John Denham, now an academic who runs the Centre for English Identity and Politics at Southampton University, offers an interesting analysis of the recent elections. The Conservatives did not do as badly as expected, and Labour did not do so well, he thinks, because of a divide between those voters who regard themselves as English and those who see their identity primarily as British.

Outside big cities and university towns, Labour gained both fewer seats than the Greens and fewer councils than the Liberal Democrats. This is because, Professor Denham suggests, Labour’s support has risen from 50 to 54 per cent among the metropolitan graduate elites, who tend to see themselves as British; support among voters who self-identify primarily as English, and who live in the former Red Wall areas which were once Labour’s heartlands, has fallen from 26 to 20 per cent. The gap is widening. To win back power, Labour needs to find out how to appeal once more to these “English” voters.

What all this suggests is that the legacy of Brexit could yet be the fragmentation of the United Kingdom into divisive national identities, from which new tensions and polarisations could flow. I’m not sure that is what anyone voted for in the Brexit referendum.