After Scotland, Northern Ireland could be heading for another referendum.

Under the1998  Good Friday Agreement, the people of Northern Ireland have a right to a poll on whether they want to remain in the UK.   No one thought it would ever be required.  But no one ever thought the UK would be leaving the EU and taking the province with it. With Article 50 now a reality, it is.The reunification of Ireland is back on the table.

Until recently, the thought of a border poll was seen as academic because of the electoral dominance in the province of the Unionist parties.  But Ulster isn’t what it was. For the first time in modern Irish history, in the recent elections following the collapse of power-sharing, Unionism lost its overall majority. Sinn Fein and the moderate nationalist Social Democratic and Labour Party now have more seats than the two Unionist parties, the Democratic Unionist Party and the Ulster Unionist Party combined. No-one yet knows what this means.

Since partition in the 1920s, the whole point of Northern Ireland was to provide a Protestant-Unionist sanctuary within Ireland. Much blood was spilled over this division, not least in the 30-year-long “troubles” which ended with the Good Friday agreement in 1998 and the creation of a devolved Stormont assembly.

Only then did the militants on both sides finally put aside their weapons. The UK Government repealed the 1920 Government of Ireland Act and said Northern Ireland would only continue to exist so long as a majority in the province wished it to.

The stability of this arrangement depended crucially on the patronage of the European Union and the Unionist community remaining the majority in Northern Ireland. It also depended on the stability of Scottish devolution. Holyrood gave the Nationalist community confidence that Britain had changed, and that the UK Government could give up power voluntarily.

Now Britain is taking Northern Ireland out of the European Union against its will, Unionism seems to be in terminal decline, and there are questions about the future of devolution in Scotland. No-one is talking about a resumption of violence – Sinn Fein is no longer simply the political wing of the Provisional IRA. But the province and the UK is clearly entering uncharted territory. The Brexit Secretary David Davis’s speculation about a border being erected in the province if there is a hard Brexit hasn’t helped.

The EU was very much a guarantor of the Good Friday Agreement, and not just because of the “peace money” and citizenship rights. It created a psychological bridge between the two communities, and between the North and the Republic. The border, so long a source of grievance, all but disappeared as North and South dissolved into the single European market, with free movement of goods and people. Brexit has blown this apart.

Nationalists in Northern Ireland want, like the SNP, to retain links with the EU, but the UK government isn’t in the mood for compromise – as the Scottish Government has learned. The UK will be leaving as one UK, with no fuzzy Celtic edges or backdoor deals.

Indeed, officials in Whitehall are now reportedly talking about “British Empire 2.0” in reference to the International Trade Secretary, Liam Fox’s proposal to create a new economic block involving the African Commonwealth. Talk like that will only inflame suspicion among Nationalists in Northern Ireland (and in Scotland) that Brexit Britain is going to be a leap into the imperial past. To those who believed that the UK was evolving into a federation this is a profound disappointment.

Right now, attention is still very much focused on trying to get devolution restarted. But the resurgent Sinn Fein may see continuation of direct rule from Westminster as the best context to build support in the province for a border poll. Brexit has left everyone thinking unthinkable, and the UK looking increasingly fragile. Indeed, we may be heading for not one, but two post-Brexit referendums.