The significance of the Cardiff Pact does not lie in any immediate change to Britain’s constitutional structure. Scotland remains part of the United Kingdom. Wales remains part of the United Kingdom. Northern Ireland remains part of the United Kingdom. No referendum was authorized, no powers were transferred, and no new constitutional institution was created on September 14, 2026. Yet treating the Cardiff Pact as merely symbolic would miss the more important development taking place beneath the rhetoric.

For the first time, the leaders of the Scottish National Party (SNP), Plaid Cymru, and Sinn Féin have formally connected their respective constitutional projects around a common principle: that Scotland, Wales, and Ireland should be able to determine their political futures through democratic means. The memorandum calls for greater cooperation among the three movements and for Westminster to “prepare for, plan and facilitate constitutional change.”^¹ At the same time, the Scottish and Welsh governments signed a separate Cardiff Agreement establishing an ongoing framework for cooperation on economic, social, environmental, international, and constitutional matters.^²

These agreements do not create a common route to independence. Indeed, the constitutional circumstances of Scotland, Wales, and Northern Ireland remain profoundly different. What they do is potentially more consequential: they begin to turn three separate disputes over national self-government into a broader dispute over the structure of the British state itself. That distinction is critical.

The question facing Westminster is no longer simply whether Scotland should become independent, whether Wales should acquire additional powers, or whether Northern Ireland might eventually reunify with Ireland. The deeper question is whether the United Kingdom’s constitutional system can continue to accommodate competing national mandates when the central government retains ultimate authority over the terms of constitutional change. The Cardiff Pact therefore represents less a constitutional rupture than a challenge to the assumptions on which Britain’s devolution settlement has rested.

From Devolution to Constitutional Contestation

The original promise of devolution was relatively straightforward: Scotland, Wales, and Northern Ireland could exercise substantial authority over domestic affairs while remaining within a common United Kingdom. That arrangement was never entirely symmetrical. The devolved institutions possess different powers, operate under different statutory frameworks, and have developed different relationships with Westminster. Northern Ireland’s settlement is additionally embedded within the international framework of the Belfast/Good Friday Agreement. Scotland and Wales operate within UK legislation governing their devolved competencies.

For much of the period since devolution, this asymmetry was politically manageable because the principal debate concerned the extent of devolved authority rather than the legitimacy of the Union itself; that equilibrium has weakened. The September 2026 Cardiff meeting occurred after elections that produced an unusual configuration: the SNP remained in government in Scotland, Plaid Cymru took control of the Welsh government, and Sinn Féin returned to a central role in Northern Ireland’s power-sharing government. All three movements support constitutional change, although their objectives and strategies differ.^³

The political significance of this configuration lies in its cumulative effect. A demand for greater Scottish autonomy can be treated as a Scottish question. A demand for Welsh independence can be treated as a Welsh question. A debate over Irish reunification can be treated as a Northern Irish question. When these demands become politically coordinated, Westminster faces a different kind of challenge. It is no longer dealing with one territorial dispute. It is confronting a broader argument that the constitutional architecture of the United Kingdom does not adequately reflect the political development of its constituent nations.

This is why the language of the Cardiff memorandum matters. The parties do not simply demand independence. They emphasize the right of each nation to determine its own future and advocate relationships between nations based on equality and mutual respect.^¹ The political argument is therefore moving from “give us more powers” toward “who has the right to determine the distribution of political power in the first place?” That is a much more fundamental constitutional question.

The Paradox of Devolution

Britain’s constitutional difficulty can be understood through a paradox. Devolution was intended to make the Union more flexible by allowing different parts of the country to govern themselves differently. Yet the success of devolution may also have created institutions capable of challenging the central state’s authority.

The Scottish Parliament, Senedd Cymru, and Northern Ireland Assembly have developed their own political cultures, electoral mandates, administrative capacities, and relationships with voters. Political competition increasingly occurs within national rather than exclusively UK-wide political frameworks.

This matters because political authority tends to acquire legitimacy through use. When voters elect governments to make decisions over health care, education, housing, taxation, economic development, and other areas of domestic policy, those governments develop an independent political mandate. Over time, the distinction between administrative autonomy and political sovereignty can become increasingly difficult to maintain.

The Cardiff Agreement between Scotland and Wales illustrates this development. It does not merely discuss independence. It establishes mechanisms for governments to share research, expertise, policy development, stakeholder engagement, and approaches to democratic participation. It also provides for regular ministerial and official-level contact and an annual meeting between the two first ministers.^² In other words, devolution is generating not only political institutions but intergovernmental capacity.

That could become important if constitutional disputes intensify. A government seeking independence does not begin with nothing. It already possesses civil servants, legislative institutions, policy expertise, administrative systems, international relationships, and experience governing a defined territory. The Cardiff Agreement potentially strengthens that institutional capacity by encouraging governments to learn from one another. This does not make independence inevitable. It does mean that the constitutional question is increasingly being debated by governments that possess the institutional resources to contemplate alternatives to the existing settlement.

The Scottish Question: Democratic Mandate Versus Westminster Authority

Scotland provides the clearest example of the tension between electoral mandates and constitutional authority. The 2014 independence referendum established an important democratic precedent. It was authorized through an agreement between the UK and Scottish governments and produced a 55.25 percent vote against independence and 44.65 percent in favor, with turnout of 84.6 percent.^⁴ The political significance of that referendum has persisted even though the result was decisive at the time.

The constitutional difficulty emerged when the SNP subsequently argued that political circumstances had changed sufficiently to justify another referendum, particularly following Brexit. Westminster rejected that argument. In 2022, the UK Supreme Court ruled that the Scottish Parliament could not unilaterally legislate for an independence referendum because the Union and the UK Parliament fall within reserved matters.^⁵ This produced an unusual constitutional situation. Scotland can elect a government committed to independence, but that government cannot itself legally initiate the referendum mechanism required to pursue independence. The result is a collision between two different understandings of democratic legitimacy.

One understanding emphasizes the constitutional authority of the UK Parliament. Under that interpretation, constitutional change must occur through the legal structures established by the United Kingdom. The other emphasizes electoral mandates and popular sovereignty. Under that interpretation, a government elected on a clear independence platform has a democratic obligation to seek a mechanism through which voters can determine the question.

Neither proposition automatically resolves the other. That is precisely why the Cardiff Pact matters. By joining the Scottish question to the constitutional demands of Wales and Northern Ireland, the agreement reframes Scotland’s dispute as part of a broader debate over whether Westminster should continue to control the mechanisms through which constituent nations can alter their constitutional status. The argument becomes less about one referendum and more about the rules governing constitutional consent.

Wales Changes the Equation

Wales introduces a different and potentially more revealing dimension. Unlike Scotland, Wales has not historically possessed the same level of mass support for independence. Yet Plaid Cymru’s control of the Welsh government represents a major development because it places an explicitly pro-independence party at the center of Welsh executive power. That creates a distinction between governing for independence and governing toward independence.

The Welsh government’s immediate responsibilities remain practical: public services, economic development, poverty, infrastructure, health, education, and the cost of living. The constitutional question must therefore coexist with the ordinary demands of government. Plaid Cymru has indicated that it does not intend to hold an independence referendum during the current Senedd term. Instead, its leadership has emphasized building the case for independence and pursuing a broader national conversation about Wales’s constitutional future.^³

That strategy is significant because it recognizes that constitutional legitimacy cannot be created solely through party declarations. If Welsh independence is to become a viable political project, its advocates will need to demonstrate what independence would mean institutionally and economically, not merely why Wales should possess greater sovereignty. The Scottish-Welsh Cardiff Agreement may provide part of that infrastructure.

Its provisions concerning economic growth, fiscal arrangements, climate policy, international engagement, democratic participation, and policy research create mechanisms through which the two governments can compare experiences and develop common expertise.^² This makes Wales more than another participant in a nationalist coalition.

It potentially becomes a laboratory for a different form of constitutional politics—one in which independence is approached gradually through the development of governing capacity, public deliberation, and institutional confidence.

Northern Ireland’s Unique Position

The inclusion of Sinn Féin creates perhaps the most interesting—and difficult—dimension of the Cardiff Pact. Northern Ireland’s constitutional future does not depend upon precisely the same mechanism as Scotland’s or Wales’s.

The Belfast/Good Friday Agreement established that Northern Ireland’s constitutional status rests upon the principle of consent. Under the Northern Ireland Act 1998, the secretary of state may call a border poll when it appears likely that a majority would support a united Ireland.^⁶ This makes Northern Ireland fundamentally different from Scotland and Wales.

Irish reunification is also connected to an international peace settlement, relations between Britain and Ireland, and the political identities of communities within Northern Ireland. The Belfast Agreement established not merely institutions of devolved government but also arrangements governing relations within Northern Ireland, between Northern Ireland and Ireland, and between Britain and Ireland.^⁷ The Cardiff Pact therefore links together constitutional questions that have very different legal foundations. That creates both an opportunity and a potential source of friction. The three movements can share a commitment to self-determination while pursuing different constitutional outcomes through different legal processes.

That distinction should not be underestimated. The alliance is strongest at the level of principle. It becomes more complicated at the level of implementation. If Scotland requires Westminster authorization for a referendum, Wales is building a political case for future constitutional change, and Northern Ireland operates under the consent provisions of the Belfast Agreement, then a coordinated timetable may be impossible. The Cardiff Pact does not need to solve that problem immediately. But if the alliance develops, it will eventually have to confront it.

Brexit Turned Constitutional Difference Into a Structural Problem

Brexit provides the broader political context in which these disputes have intensified. The 2016 referendum produced a UK-wide result even though political preferences differed substantially across the four nations. Scotland voted to remain in the European Union, as did Northern Ireland, while England and Wales voted to leave.

The constitutional consequence was not simply Britain’s withdrawal from the EU. It was the demonstration that a single UK-wide electoral mandate could produce a policy outcome that significant national electorates opposed. For supporters of greater autonomy, Brexit became evidence that the existing constitutional system could allow Westminster-level decisions to override distinct national preferences.

The Cardiff memorandum explicitly connects constitutional autonomy with Europe. The parties argue that Brexit damaged economic opportunities and call for stronger relationships with the European Union.^¹ But here again, the political argument is easier than the institutional one. An independent Scotland would have to negotiate its relationship with the EU. An independent Wales would face its own negotiations. Northern Ireland’s position is different because the Republic of Ireland is already an EU member and because the Belfast Agreement provides a specific framework for constitutional change. Thus, Europe provides a common political aspiration without providing a common constitutional pathway. That distinction is important because it points toward the larger challenge facing the Cardiff alliance: shared opposition to Westminster is easier to sustain than agreement on what should replace Westminster’s constitutional role.

The Economic Argument Will Eventually Become Unavoidable

The constitutional debate cannot remain at the level of sovereignty indefinitely. If the Cardiff Pact develops into a serious political project, economic questions will become unavoidable. Independence or constitutional restructuring would raise questions about public debt, pensions, taxation, currency, trade, energy, defense, financial regulation, infrastructure, and public administration. Those questions are particularly important because Scotland, Wales, Northern Ireland, and England are deeply economically integrated.

Businesses operate across borders. Workers live in one jurisdiction and work in another. Energy systems cross territorial boundaries. Supply chains are integrated. Public institutions cooperate across jurisdictions. Changing constitutional boundaries would therefore create a period of institutional negotiation regardless of the political outcome. This is where the Cardiff Agreement could become more important than the party memorandum.

The government agreement encourages joint research, policy development, evidence-sharing, and cooperation on economic and fiscal questions.^² If those mechanisms produce serious comparative research on fiscal capacity, energy systems, trade, social policy, or public administration, the constitutional debate could gradually move from political aspiration toward institutional preparation. That would represent a significant shift. The central question would no longer be merely whether independence is possible. It would become: what would the institutions of independence—or a radically reformed Union—actually look like?

The Missing Question Is England

There is, however, a fundamental omission from the Cardiff framework. The constitutional future of the United Kingdom cannot be reconstructed solely through negotiations among Scotland, Wales, and Northern Ireland. England contains the overwhelming majority of the UK’s population and economic activity. Any change to the territorial constitution would necessarily alter England’s political position.

This creates a problem for both sides of the debate. Nationalist movements understandably focus on the constitutional rights of their own nations. Westminster, meanwhile, tends to frame the issue around the preservation of the United Kingdom as a whole. But neither approach fully addresses the constitutional position of England.

• If Scotland and Wales become independent, what constitutional relationship would England establish with them?
• If Britain becomes a federal state, what institutions would represent England? If Northern Ireland reunifies with Ireland, how would the remaining United Kingdom be structured?
• If devolution expands without independence, would England receive equivalent regional institutions?

These are not peripheral questions. They are central to the future constitutional architecture of the state. The absence of England therefore illustrates a deeper problem with the current constitutional debate: Britain has developed institutions for national self-government without creating a comprehensive constitutional framework for the relationship among those governments. The Cardiff Pact exposes that gap. The constitutional question is ultimately larger than the nationalist movements. It is a question about the future structure of the British state.

From Territorial Dispute to State Redesign

This is ultimately why the Cardiff Pact deserves attention. Its importance does not depend on whether Scotland becomes independent, Wales becomes independent, or Northern Ireland joins a united Ireland. The more significant possibility is that the pact accelerates a shift in the political debate from territorial separation to constitutional redesign.

There are several possible outcomes. One is continued centralization within the existing Union. Another is deeper devolution, giving Scotland, Wales, and Northern Ireland greater fiscal and legislative autonomy. A third is some form of federal or quasi-federal United Kingdom. A fourth is negotiated independence for one or more constituent nations. A fifth is a more complex arrangement in which different territories acquire different constitutional relationships with Westminster and with one another.

The Cardiff Pact does not choose among these alternatives; its language leaves considerable room for them. That ambiguity may be politically useful. It allows different movements to cooperate without resolving questions they are not yet ready to answer. However, if the pact develops, its leaders will eventually have to explain not simply what they want to leave behind, but what they want to build.

Westminster’s Strategic Choice

The British government’s response will therefore matter enormously. Westminster can treat the Cardiff Pact as an expression of nationalist politics and continue to argue that the Union is the appropriate framework for addressing economic and social problems.

The government has emphasized cooperation among the four nations and said that its priority is economic security rather than constitutional debate.^³ That position has an internal logic. A government can argue that constitutional change should not become a substitute for governing. It can also argue that constitutional questions should be settled through established legal mechanisms rather than political pressure. However, there is a risk in treating constitutional demands solely as distractions.

The more national governments develop their own policy capacity and political identities, the more difficult it may become to preserve a constitutional system in which ultimate authority remains concentrated at Westminster. The alternative is not necessarily to concede independence.

Westminster could instead pursue constitutional reform before demands for separation become the only meaningful form of national self-government. That could involve strengthening intergovernmental relations, clarifying the division of powers, reforming fiscal arrangements, establishing clearer procedures for constitutional referendums, or developing a more explicitly federal settlement. Such reforms would not guarantee the survival of the Union. But they could change the political terms on which its future is debated.

The Cardiff Pact’s Real Test

The ultimate test of the Cardiff Pact will therefore not be another summit or another declaration. It will be whether the participating governments and parties can transform political solidarity into institutional capacity.

• Can they develop serious economic research?
• Can they demonstrate how energy systems would function across new constitutional boundaries?
• Can they explain how fiscal arrangements would work?
• Can they address defense and international relations?
• Can they develop credible plans for trade with the remainder of the United Kingdom?
• Can they establish mechanisms for resolving disputes among the constituent nations?
• Can they persuade voters who are not already committed nationalists that constitutional change would produce a workable political settlement?
• Can Westminster respond with something more substantive than either rejection or defense of the status quo?

Those questions move the debate beyond nationalism. They make it a question of governance. That is why the Cardiff Pact could become important even if none of the three constitutional projects immediately succeeds. It has the potential to force British politics to confront the question : Can a multinational state remain politically legitimate when its constituent nations increasingly possess distinct political mandates but the central government retains ultimate constitutional authority? That is the real test of Cardiff.

Conclusion: The Beginning of a Constitutional Conversation

The Cardiff Pact is neither the dissolution of the United Kingdom nor an empty political gesture. Its significance lies between those two interpretations. It represents an effort to connect three constitutional movements that have historically developed along separate paths. More importantly, the simultaneous Scottish-Welsh government agreement creates an institutional framework through which cooperation can continue beyond the symbolism of a single summit.^¹²

The immediate political objectives remain different. Scotland faces the question of whether Westminster will permit another independence referendum. Wales is at an earlier stage of developing a political case for independence. Northern Ireland operates under a distinct consent-based framework for determining its constitutional future. For Westminster, the challenge is no longer simply to defend the Union against individual nationalist movements. It is to demonstrate that the Union can provide a constitutional structure capable of accommodating competing national identities, democratic mandates, and demands for political autonomy.

For Scotland, Wales, and Northern Ireland, the challenge is equally substantial. Political demands for self-determination must eventually be accompanied by credible answers about institutions, economics, governance, and relations with the populations and governments with which they remain deeply interconnected. The Cardiff Pact has therefore not answered Britain’s constitutional question. It has made the question harder to postpone.

The next phase of the debate will not be determined simply by declarations of independence or defenses of the Union. It will be determined by competing visions of what should replace the existing constitutional settlement—or how that settlement should be transformed.

That is the real significance of Cardiff. It has moved the debate one step closer to the question that Britain has spent decades avoiding: not simply whether the Union should survive, but what kind of constitutional order could make survival politically sustainable.

Notes

1. Sinn Féin, “Leaders of Plaid Cymru, SNP and Sinn Féin Agree Memorandum of Understanding to Build Towards Constitutional Change,” September 14, 2026, https://sinnfein.ie/news/leaders-of-plaid-cymru-snp-and-sinn-fein-agree-memorandum-of-understanding-to-build-towards-constitutional-change/.

2. Welsh Government, “The Cardiff Agreement – Cytundeb Caerdydd between the Welsh Government and the Scottish Government,” September 14, 2026, https://www.gov.wales/the-cardiff-agreement-cytundeb-caerdydd-between-the-welsh-government-and-the-scottish-government-html.

3. ITV News Wales, “Nationalist Leaders of Devolved Governments to Hold Summit in Cardiff,” September 14, 2026, https://www.itv.com/news/wales/2026-09-14/nationalist-leaders-of-devolved-governments-to-hold-summit.

4. Electoral Commission, “Report: Scottish Independence Referendum,” https://www.electoralcommission.org.uk/research-reports-and-data/our-reports-and-data-past-elections-and-referendums/report-scottish-independence-referendum.

5. UK Supreme Court, Reference by the Lord Advocate of Devolution Issues, [2022] UKSC 31, November 23, 2022, https://www.supremecourt.uk/cases/uksc-2022-0098.

6. House of Commons Library, Northern Ireland: Border Polls, Research Briefing CBP-10101, June 24, 2025, https://commonslibrary.parliament.uk/research-briefings/cbp-10101/.

7. Northern Ireland Office, The Belfast Agreement, April 10, 1998, https://www.gov.uk/government/publications/the-belfast-agreement.

Bibliography

Electoral Commission. “Report: Scottish Independence Referendum.” https://www.electoralcommission.org.uk/research-reports-and-data/our-reports-and-data-past-elections-and-referendums/report-scottish-independence-referendum.

House of Commons Library. Northern Ireland: Border Polls. Research Briefing CBP-10101. June 24, 2025. https://commonslibrary.parliament.uk/research-briefings/cbp-10101/.

Northern Ireland Office. The Belfast Agreement. April 10, 1998. https://www.gov.uk/government/publications/the-belfast-agreement.

Sinn Féin. “Leaders of Plaid Cymru, SNP and Sinn Féin Agree Memorandum of Understanding to Build Towards Constitutional Change.” September 14, 2026. https://sinnfein.ie/news/leaders-of-plaid-cymru-snp-and-sinn-fein-agree-memorandum-of-understanding-to-build-towards-constitutional-change/.

UK Supreme Court. Reference by the Lord Advocate of Devolution Issues. [2022] UKSC 31. November 23, 2022. https://www.supremecourt.uk/cases/uksc-2022-0098.

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