The leaders of Scotland, Wales and Northern Ireland are expected to meet in Cardiff with Mary Lou McDonald and likely sign a declaration on self-determination. The summit could add pressure on Westminster as disputes over independence referendums and Irish unity move higher up the political agenda.

Westminster may still regard the United Kingdom as the settled constitutional order, but the politics beyond are telling a different story. Scotland, Wales and Northern Ireland are being led by parties that question some part of that settlement, and their leaders are now preparing to turn their shared interests into a coordinated project.

According to The Telegraph, the three first ministers will meet in Cardiff on Monday to sign a joint declaration on self-determination, joined by Sinn Fein president Mary Lou McDonald. Their message is likely to be uncomfortable for Westminster: the union cannot simply be assumed to endure if its constituent nations increasingly want the right to decide their own futures.

Scotland’s First Minister John Swinney and Wales’ First Minister Rhun ap Iorwerth, alongside Northern Ireland’s leadership, are expected to sign a joint declaration asserting their nations’ right to self-determination, including the right to pursue independence through democratic means.

The meeting will be held at the five-star St David’s Hotel overlooking Cardiff Bay. The leaders are expected to discuss a fresh political campaign around independence, while seeking closer cooperation on the economy, energy, Europe and international affairs. The summit takes place at a politically sensitive moment for the UK, after Prime Minister Andy Burnham indicated that another Scottish independence referendum could be considered if there were a “clear consensus” for one.

The gathering also follows US President Donald Trump’s intervention in the Irish unity debate. During his visit to Dublin on Saturday, Trump said he would “love” to see a united Ireland and described reunification as a potentially “fantastic thing”.

PRO-INDEPENDENCE FORCES GAIN GROUND

The Cardiff meeting has gained added significance after recent elections strengthened the position of parties advocating greater autonomy or independence. Labour’s poor performance in Wales at May’s elections allowed Plaid Cymru to emerge as the largest party in the Cardiff Senedd, with its leader Rhun ap Iorwerth becoming first minister.

In Scotland, the SNP remains the dominant force despite losing six seats at Holyrood, while Reform and the Greens made gains.

Northern Ireland presents a different constitutional picture but has also seen Sinn Fein consolidate its political position. The party won the 2022 Stormont election, although a DUP boycott delayed the formation of a functioning executive until 2024, when Michelle O’Neill became first minister.

Sinn Fein is widely expected to remain in power after the next Northern Ireland election.

The alignment means Scotland, Wales and Northern Ireland now have leaders from parties that support significant constitutional change or Irish reunification, creating an opportunity for closer coordination between the devolved administrations and nationalist movements.

Swinney has seized on the development, arguing that the landscape shows the UK’s existing constitutional arrangement is under growing pressure.

“For the first time ever, Scotland, Wales and Northern Ireland are led by pro-independence first ministers. There could be no clearer sign that the status quo is not sustainable – and that Westminster must prepare for a post-UK future,” he said, as per The Telegraph.

“The momentum behind serious constitutional change is undeniable. Andy Burnham must now be facing up to the idea that he will go down in history as the final prime minister of the United Kingdom,” he added.

BURNHAM’S SCOTLAND COMMENTS FUEL ROW

Burnham’s recent remarks about a possible Scottish independence referendum are expected to be the main issue at the Cardiff summit.

Speaking in the House of Commons, Burnham said another vote could take place if there was a sufficiently clear public consensus behind it. His comments have been seized upon by the SNP as evidence that Westminster’s position on Scottish independence is shifting.

However, Burnham has since sought to draw a line under speculation that a referendum could take place in the near future.

In a letter to Swinney sent on Thursday, he said another Scottish independence referendum was “off limits” before the next general election. Burnham also argued that there was “no consensus for an independence referendum in Scotland and nor is there a clear basis to suggest that a majority of people in Northern Ireland presently wish to separate from the United Kingdom”.

He wrote: “The 2024 manifesto on which Labour secured its parliamentary majority was unambiguous: ‘Labour does not support independence or another referendum.’

“As I made clear to you personally when we met recently in Glasgow, independence and a referendum are off limits as it would take our focus away from growing the economy and helping families with the cost of living.”

Swinney, however, has continued to attack the prime minister’s handling of the constitutional question.

A source close to the Scottish first minister told The Telegraph: “He (Burnham) f***ed up by using the Scottish line in Northern Ireland then this week f***ed up again by using the Northern Ireland line about Scotland.”

He also criticised Burnham’s handling of the constitutional issue, arguing that his recent comments showed a lack of understanding of the UK government’s position on the Union and could alarm supporters of the UK’s territorial integrity.

GOOD FRIDAY AGREEMENT HOLDS KEY

The Irish dimension adds another layer to Monday’s discussions.

Under the 1998 Good Friday Agreement, Northern Ireland’s constitutional future can be put to a public vote if it appears likely that a majority would support leaving the UK and joining a united Ireland.

That provision was central to the peace settlement that helped end decades of sectarian violence known as the Troubles. The agreement allows constitutional change to be pursued through democratic means rather than conflict.

A Sinn Fein source said the Cardiff discussions would focus on each nation’s ability to determine its future democratically.

Trump’s comments in Dublin have added attention to the issue.

“Well, I don’t want to cause any trouble, but I will tell you, I’d love to see it unified,” Trump told reporters at Farmleigh House in Dublin. “It’s going to happen eventually. I think it will be a fantastic thing.”

“Now the UK will have something to say about it, obviously, but I think it would be a great thing,” he added. The remarks represented a departure from the traditionally cautious approach taken by US Presidents on Irish reunification.

ECONOMY, ENERGY AND EUROPE ALSO ON THE AGENDA

The Cardiff agreement is expected to go beyond the question of independence.

As per the report, the leaders will sign a memorandum of understanding committing their parties to cooperate in areas including the economy, energy, Europe, international cooperation and self-determination.

The three parties are expected to support membership of the European Union for their respective nations — with Scotland and Wales joining as new members and Northern Ireland becoming part of Ireland in the event of reunification. The agreement is also expected to call for stronger ties with European neighbours as the parties develop their plans for potential independence.

Plaid Cymru is also expected to press Westminster for greater powers over Welsh taxation and spending. Among its demands is control over revenues from the Crown Estate, including seabed areas used for offshore wind projects.

The party is also seeking changes to the Barnett Formula, as well as greater devolved powers over areas including policing and rail funding.