Ten years after the Brexit referendum: A relationship without a destination

A decade has passed since British citizens voted to leave the EU – a decade in which Europe’s world has been turned upside down. Leaders across European capitals, including London and Brussels, openly acknowledge the strategic case for closer ties. Yet remarkably little has changed in the relationship between the EU and the UK. Europe’s leaders and institutions understand the need to work together with the UK. But the lack of meaningful action suggests that the current approach may be a dead end. 

In the months after the 2016 referendum, many scholars, commentators and practitioners – myself included – believed that a new EU-UK relationship should start with security and defence. Economic and trade talks were always likely to make for a difficult, lopsided negotiation. After all, European integration has gone furthest in the economic sphere, through the single market, and any negotiation between a 27-member union and a single European country, however large, was bound to be asymmetrical. 

Security and defence appeared to offer a more fertile ground. The UK remained one of Europe’s leading military powers, with a nuclear deterrent, significant armed forces and a developed strategic culture. By contrast, EU countries had collectively long struggled to turn their military ambitions into concrete actions. There was an obvious case for a mutually beneficial partnership. But this never materialised, not least because the Conservative governments of those years ruled out any structured engagement with the EU in this area. 

Since then, Europe has lurched from crisis to crisis. It faces Russia’s war in Ukraine and its wider imperial ambitions in eastern Europe. It faces a United States that, under the second Trump administration, has not merely disengaged from European security but actively betrayed European trust in the transatlantic alliance – most egregiously over Ukraine and through its threats to use force to take Greenland. Across Europe, far-right forces have received support from both Russia and the MAGA movement. European leaders have long acknowledged that these interlinked threats can only be overcome if the EU and the UK act together. 

"The time has come to admit that the current approach has reached its limits.”

The change of government in London in July 2024 created an opportunity to reset the relationship. Many hoped that both sides were finally willing to turn the page. After all, the EU and the UK share the same strategic outlook and support for Ukraine after Russia’s full-scale invasion. When British and EU leaders met at Lancaster House in May 2025, at the first such summit since Brexit, they agreed an EU-UK security and defence partnership, which was modelled on the EU’s agreements with other ‘like-minded partners’ such as Norway. The partnership, in principle, opened the door to British participation in Security Action for Europe (SAFE) – a €150 billion loan fund supporting defence projects involving several EU member-states or third countries with a partnership agreement. And while the ‘reset’ promised future deals on agrifood trade, carbon pricing and youth mobility, it was the need for closer co-operation on security and defence that gave the effort its strategic purpose. 

A year later, the record is mixed. The UK and the EU remain practically aligned on most major foreign and security policy issues. The security situation has not improved: hopes for a ceasefire in Ukraine are fading; the transatlantic rupture is deepening, particularly since the Greenland crisis; and despite a fragile ceasefire, the US-Israeli attack on Iran has created bloody chaos in the Middle East and closed the economically vital Strait of Hormuz. Collective European action, often with the UK co-leading alongside France, has emerged through coalitions of the willing operating outside existing EU and NATO frameworks. Yet there is still little to report on EU-UK co-operation. Negotiations over the UK’s participation in SAFE first failed at the end of last year. They were restarted this year, but have not yet delivered an agreement. 

Where proposals have emerged, such as the UK’s recent suggestion to re-enter parts of the single market for goods, they have been underwhelming, because the free movement of goods is only one of the four freedoms in the single market. The UK has attempted to cherry-pick from the EU since Brexit. One wonders what makes London believe that doing the same thing over and over again will lead to a different response from Brussels.  

This raises a difficult question: is it time to acknowledge that there are critical, perhaps insurmountable, limits to the depth and breadth of the EU-UK relationship so long as membership remains expressly excluded? 

In Britain, ruling out membership emboldens committed Brexiteers to obstruct closer cross-Channel ties, while placing supporters of deeper integration on the defensive. Pro-Europeans are left advocating incremental improvements while avoiding a larger argument about the country’s future, for fear of being misunderstood. In Brussels, meanwhile, Britain’s rejection of membership consigns it to the category of a third country: an important partner but never a genuine priority. This is not out of spite towards the UK. More crudely, it is because relations with the UK are not perceived as being as important as those with the US, China or other major powers, whose economic and political leverage over the EU is far greater than that of the UK. 

Nor are relations considered fraught enough to compel Brussels to go the extra mile. European leaders remain wary of offering the UK a privileged arrangement that could set an unwelcome precedent for member-states tempted by opt-outs of their own. Even a decade after the Brexit referendum, those instincts are deeply embedded in the EU’s institutional thinking. There is simply no incentive for the EU to offer meaningful concessions – and little, if any, leverage through which the UK can cajole the EU to do so. 

Two years after the Labour government announced the reset, the time has come to admit that the current approach has reached its limits. Unless the UK embarks on a path that treats membership as a genuine possibility, the structural limits of the relationship will continue to outweigh the political case for any strategic convergence across the Channel. In today’s world, neither side can afford that.

Nathalie Tocci is professor of practice at the Johns Hopkins University SAIS, a former special adviser to EU High Representatives for Foreign Affairs, and a member of the CER’s advisory board. 

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