The leaders of Wales, Scotland and Northern Ireland are to sign a joint declaration affirming their countries' right to seek independence from the United Kingdom at a landmark summit in Cardiff on Monday. The memorandum of understanding will call on Westminster «to prepare, plan and facilitate constitutional change in Wales, Scotland and Northern Ireland», according to the text of the agreement.
The signatories are expected to be Plaid Cymru leader Rhun ap Iorwerth, Scottish National Party leader John Swinney and Sinn Féin vice-president Michelle O'Neill. The three party leaders will meet in the Welsh capital to formalise the declaration, which represents a significant co-ordination of the pro-independence and pro-constitutional-change positions across the three Celtic nations.
The summit is likely to challenge Andy Burnham's devolution agenda, which has focused on transferring powers to English regions and combined authorities rather than addressing the constitutional status of the devolved nations. The declaration places the question of independence and broader constitutional reform firmly back on the political agenda at a time when the UK government has consistently resisted calls for a second Scottish independence referendum.
The memorandum of understanding does not itself trigger any referendum or binding process, but it signals a shared intent among the three administrations to press for a formal mechanism by which constitutional change could be delivered. By framing the demand as a call on Westminster to «prepare, plan and facilitate» change, the leaders are seeking to shift the burden of action to the UK government and to establish a common front that is harder to dismiss as a single-nation grievance.
The timing of the Cardiff meeting places the declaration in direct tension with the devolution model favoured by Burnham, who has argued that economic and political power should be redistributed within England as a counterweight to centralisation in London. The Celtic leaders' intervention suggests that devolution within England, however ambitious, does not satisfy the demands for self-determination in Scotland, Wales and Northern Ireland.
For Sinn Féin, the declaration aligns with its long-standing position on Irish unity and its participation in the Northern Ireland Executive. For the SNP, it reinforces the party's central argument that Scotland's future should be decided in Scotland. For Plaid Cymru, it marks a further step in the party's evolution from a pressure group for Welsh language and cultural rights into a movement explicitly campaigning for Welsh independence.
The summit also raises questions about the internal dynamics of the UK's territorial constitution. The three leaders represent parties that hold power in their respective devolved administrations, giving the declaration an official character that goes beyond opposition rhetoric. While the UK government is not bound by the memorandum, the document will be cited by pro-independence campaigners as evidence of a cross-nation consensus on the right to choose.
Unionist parties in Scotland and Northern Ireland are likely to criticise the declaration as an attempt to bypass the results of previous referendums and to undermine the principle that constitutional change requires broad consent. The UK government has repeatedly stated that the 2014 Scottish independence referendum was a once-in-a-generation event and that there is no case for another.
Monday's meeting in Cardiff is expected to conclude with a public statement and the formal signing of the memorandum. The three leaders will then face the task of translating the declaration into practical political pressure, including through intergovernmental mechanisms and parliamentary lobbying at Westminster. Whether the joint front holds will depend on how each party balances its domestic priorities with the shared demand for constitutional change.