What would happen if Scotland, Wales and Northern Ireland became independent?

The prospect of Scotland, Wales and Northern Ireland leaving the United Kingdom has moved back into the political spotlight. Today, the first ministers of the three nations are expected to affirm their right to pursue self-determination at a summit in Cardiff. The meeting is politically significant, but it is important to distinguish between declaring a right to independence and actually becoming independent. The latter would require a lengthy constitutional and political process, negotiations with Westminster and, in most circumstances, a clear democratic mandate from voters.

The first complication is that there is no single UK law setting out a general procedure by which any part of the United Kingdom can simply declare independence. The UK constitutional system is based heavily on parliamentary sovereignty, while Scotland, Wales and Northern Ireland operate under different devolution settlements. This means that the legal route would be different for each country.

Scotland

Scotland already has a clear precedent for an independence referendum. In 2014, voters were asked whether Scotland should become an independent country, and 55% voted to remain in the UK. That referendum was agreed between the UK and Scottish governments, with a temporary Section 30 Order transferring the necessary authority to the Scottish Parliament. The arrangement was intended to put the legality of the referendum beyond serious dispute.

Under the current legal position, the Scottish Parliament cannot simply legislate for another binding independence referendum on its own. The UK Supreme Court ruled in 2022 that legislation for an independence referendum concerned a matter reserved to Westminster and therefore fell outside Holyrood's legislative competence. In practical terms, Scotland would need an agreement with the UK government and Parliament for another legally secure referendum, unless the constitutional framework itself were changed.

If Westminster agreed to another referendum and a majority of Scots voted for independence, the result would not mean that Scotland became independent the following day. The two governments would then have to negotiate the terms of separation. Those negotiations could cover the division of UK assets and debts, borders, pensions, defence, currency, trade, citizenship, energy, public-sector institutions and Scotland's future relationship with the rest of the UK. The 2014 process provides an indication of the sort of issues that would have to be addressed, although independence negotiations could be much more extensive.

Wales

Wales faces a different legal situation. Unlike Scotland, it has never held a referendum on independence. The Senedd has significant devolved powers, but the fundamental constitutional status of Wales remains a matter for the UK constitutional framework. The Welsh Government therefore could not simply pass an Act declaring Wales independent and expect it to have legal effect.

A realistic route would involve Westminster agreeing to a referendum, either through legislation or an agreed constitutional mechanism. If Welsh voters then chose independence, negotiations would follow. Wales would have to establish the institutions required of an independent state, including responsibility for areas currently handled at UK level.

That would be a particularly substantial change because independence would transfer powers currently exercised by Westminster and UK-wide institutions to the Welsh state. Questions would include how Wales would fund pensions and welfare, how it would manage taxation and borrowing, what currency it would use, how it would handle defence and foreign affairs, and what trading relationship it would have with England and the wider UK.

Northern Ireland

Northern Ireland is legally different from both Scotland and Wales because its constitutional future is specifically addressed by the 1998 Good Friday Agreement. The agreement established the principle that the constitutional status of Northern Ireland should depend on the consent of its people. Under the Northern Ireland Act, the Secretary of State has the power to call a border poll and must do so if it appears likely that a majority of people in Northern Ireland would vote for a united Ireland.

This means that Northern Ireland does not need exactly the same legal mechanism as Scotland. A vote would concern whether Northern Ireland should cease to be part of the UK and become part of a united Ireland, rather than establishing an entirely new independent Northern Irish state. If a majority voted for unity, further negotiations would be required between the UK and Irish governments and other relevant parties to implement the constitutional change.

Therefore, there is an important distinction between the three cases. Scotland and Wales are primarily discussing independence from the UK, while Northern Ireland has a treaty-backed route towards Irish reunification. The political declaration being discussed by the three first ministers may put them under the same broader banner of self-determination, but their legal routes are not identical.

What would happen if all three voted to leave?

If Scotland, Wales and Northern Ireland all chose to leave the UK, the consequences would be enormous. The United Kingdom as it currently exists would effectively cease to operate in its present form, leaving England as the largest remaining constituent nation. It would also raise difficult questions about the future of the UK Parliament, monarchy, international treaties, armed forces and national debt.

One of the biggest challenges would be dividing assets and liabilities. The UK government owns military bases, government buildings, infrastructure and other assets throughout the country. It also has substantial public debt and long-term financial obligations, including state pensions. An agreement would be needed on how those responsibilities were divided. There would probably be lengthy arguments over whether assets and debts should be divided according to population, geography, contribution to the UK economy or another formula.

The future of the British armed forces would also have to be negotiated. For example, the independence of Scotland would raise questions about military bases and defence installations located there. An independent Scotland would have to decide whether to establish its own armed forces or enter into defence arrangements with neighbouring countries. Wales and a newly unified Ireland would face their own questions about defence and security.

Currency would be another major issue. An independent Scotland could seek to continue using the pound, establish its own currency or potentially pursue another arrangement. Wales would face similar questions about its monetary system. None of the countries would automatically inherit membership of the European Union simply by becoming independent. If they wanted to join the EU, they would have to go through the accession process and satisfy the relevant conditions.

Borders and everyday life

For ordinary people, one of the most immediate questions would be whether independence actually meant a hard international border. It would not necessarily have to. The new countries and the remaining UK could agree to keep borders relatively open, allowing people to live, work and travel freely across them. But such arrangements would have to be negotiated.

Trade would be particularly important because England and the new states would remain extremely close economically. Millions of people live and work across internal UK borders, while companies depend on supply chains that currently operate without international customs checks. Independence could therefore create pressure for agreements designed to keep trade and movement as easy as possible.

Citizenship would also need to be settled. People living in Scotland, Wales and Northern Ireland currently hold British citizenship. Independence would raise questions over whether they would automatically become citizens of their new countries, whether they could retain British citizenship, or whether people would be allowed to hold dual citizenship. These questions could become especially complicated for families with connections to more than one part of the former UK.

It would not happen quickly

Perhaps the most important point is that the meeting today would be the beginning of a political process, not the breakup of the UK itself. Even if the three governments agree that their peoples have a right to self-determination, they cannot simply dissolve the United Kingdom overnight.

The immediate objective is likely to put political pressure on Westminster to accept a clearer democratic route towards referendums. The Scottish government has already called for an agreed legal mechanism governing when an independence referendum could take place, after recent comments by Prime Minister Andy Burnham about Scotland's position. Downing Street has so far resisted allowing another Scottish referendum.

If the UK government eventually agreed to referendums, voters would have the decisive say. A successful vote would then be followed by negotiations lasting potentially several years. Independence would only become a legal reality once the necessary legislation, agreements and constitutional arrangements had been completed.

In the end, the most significant development today is not that Scotland, Wales or Northern Ireland are about to leave the United Kingdom. They are not. The significance is that the leaders of all three devolved governments are attempting to establish a common political argument that the people of each nation should have the democratic right to determine their own constitutional future.

Whether Westminster accepts that argument, and whether voters choose independence or reunification, will determine whether the meeting today becomes the beginning of the disintegration or simply another chapter in the long-running constitutional debate.