Could a Scottish, Welsh and Northern Irish independence pact threaten UK unity?

Leaders of the main Scottish, Northern Irish and Welsh nationalist parties declared at a meeting overnight that they have the right to choose whether to stay in the United Kingdom, with all three seeing their future as nations within the European Union.

The Scottish National Party (SNP), Plaid Cymru in Wales, and the pro-Irish-unity Sinn Féin want to break away from the UK, although under different timelines and conditions.

The rare meeting in the Welsh capital came just days after United States President Donald Trump waded in on the issue, saying he would back a united Ireland.

His comments showed "the unity debate is very much alive", Northern Ireland's Michelle O'Neill said alongside fellow party leaders as they announced a memorandum of understanding.

"Our nations have the right to self-determination. No Westminster government (the UK government) has the right to block democracy or undermine the principle that our people will decide their own future," the agreement said.

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SNP leader John Swinney, Rhun ap Iorwerth, leader of Plaid Cymru in Wales, and Mary Lou McDonald and O'Neill, leader and deputy leader of Sinn Féin, met in their roles as party leaders, rather than as top officials in their respective governments.

O'Neill is Northern Ireland's first minister while Iorwerth and Swinney lead their respective nationalist parties in Scotland and Wales.

The agreement said that, for the first time, each nation had a first minister "committed to independence from the UK", adding: "The future of our nations belongs in the European Union."

The independence parties are the biggest in both the Scottish and Welsh parliaments for the first time since devolution measures began in 1999. Sinn Féin has been the biggest party in Northern Ireland's assembly since 2022.

The SNP wants a second independence referendum after an earlier ballot in 2014 saw Scotland narrowly vote to remain in Britain. Successive UK governments have ruled out an immediate rerun.

Sinn Féin, the former political wing of the paramilitary Irish Republican Army (IRA), wants a vote on the UK territory of Northern Ireland being reunified with Ireland.

Plaid Cymru seeks Welsh independence in the longer term, but Iorwerth has ruled out pressing for a referendum immediately.

Laura McAllister, a politics professor at Cardiff University, said the deliberately broad term "self-determination" was used due to these differing timelines and goals.