The historic UK-EU trade deal secured on December 24 is seen by many as the end of Brexit. Yet, the huge, wide-ranging processes unleashed by Britain’s 2016 referendum are only just beginning to play out in ways that could have contrasting implications for the European Union and United Kingdom. While the 2020s could potentially see a more federal, centralised EU after the UK’s departure, the opposite may be true for the UK itself. With pressures growing for Scottish independence and potentially even Irish reunification, these are uncertain times for the union of England, Scotland, Wales and Northern Ireland. The immediate backdrop for this is December 24’s trade breakthrough which is, mostly, welcome news for European and wider global business after more than four years of Brexit uncertainty. However, this is tempered by the fact that the agreement is the first international trade negotiation in history where barriers go up, rather than down, compared to the status quo, and it does not cover the services sector, which accounts for 80 per cent and 70 per cent respectively of the UK and EU economies. Much attention, in the past half decade, has focused on these trade (and the earlier withdrawal) negotiations between the EU and United Kingdom. This has obscured the fact that the UK referendum set off a much wider set of changes. Indeed, the EU-UK trade talks are, in fact, only one subset of much broader, forward-looking debates in four areas: between the EU and the UK; within the UK; within the EU; and, also between the UK, EU and the rest of the world. Take the example of the EU-UK discussions on their future relationship. Important as the Christmas Eve deal is, there are key holes in it, not just for economic sectors like financial services, but also other critical areas of cooperation, including foreign and defence policy, which had originally been proposed to be in the agreement. Britain waking up to consequences of bungled Brexit, pandemic Moving beyond the EU-UK negotiations, Brexit has also set off important debates within the UK; within the EU about its future; and also between the UK, EU and the rest of the world. Within the EU, for instance, there are several key debates about the 27-member bloc’s future well under way, including rebalancing the union given the new balance of power within it, and whether the EU now integrates further, disintegrates or muddles through. For instance, with the UK no longer in the Brussels-based club, the EU 27 has already made significant steps last year towards greater federalism. One example is the new €750 billion (US$825 billion) coronavirus recovery fund , a major political milestone in the post-war history of European integration, which saw the continent’s presidents and prime ministers commit for the first time to the principle of jointly issued debt as a funding tool. This potentially paves the way for greater, future EU supranational powers of taxation, altering the political economy of the union, post-Brexit. In the UK, there are also major internal debates about the future. However, whereas the next few years may result in a stronger, centralised union of EU states (despite significant continuing disagreements), the opposite may be true across England, Scotland, Wales and Northern Ireland. Brexit has exacerbated tensions over the UK’s unity in several ways, including putting Northern Ireland at the forefront of UK politics in a way it had not been since the Good Friday Agreement just over two decades ago. UK Prime Minister Boris Johnson’s decision to allow a new border between Northern Ireland and the rest of the UK has angered much of the unionist community, especially the Democratic Unionist Party (DUP). This, combined with the 2019 UK general election result which saw the nationalist parties, Sinn Fein and the Social Democratic and Labour Party, win nine seats in Westminster compared to the DUP’s eight seats, has given rise to speculation as to how soon a referendum might be held on Irish reunification. While Northern Ireland was relatively muted as an issue during the 2016 referendum, the prospect of Brexit leading to Scottish independence was actively debated. Now the 2019 Westminster election result and the Scottish National Party’s continued political strength in the Scottish legislature could mean a new independence referendum. Brexit boosts Scottish movement to end London’s rule Growing tensions with the rest of the UK are almost inevitable. The SNP has asked Johnson to agree to a new independence vote. His decision to reject the request to date deals with the issue in the immediate term; however, the SNP is playing a longer game, expecting to dominate results in the 2021 Scottish elections, after which this issue could come to the boil. Taken together, this is why the short- to medium-term implications of Brexit could have significantly different implications for Brussels and London. While both unions are under stress, the 2020s could yet see a tighter, increasingly federal EU while the United Kingdom could become significantly more decentralised or even broken up, given the growing threat to its territorial integrity. Andrew Hammond is an associate at LSE IDEAS at the London School of Economics