Michel Barnier, the EU's former chief Brexit negotiator, appeared at a Chatham House event to discuss the tenth anniversary of Brexit and the trajectory of UK-EU relations — a moment that landed against a measurably changed public mood on both sides of the Channel.

Barnier has long held a firm position on the boundary between security cooperation and trade leverage. As far back as May 2018, he warned explicitly against treating security and defence policies and capabilities as chips in EU-UK negotiations — a line he has maintained since. That position carries renewed weight now. EU Institute for Security Studies research from June 2021 documented the structural gap Brexit left in the EU's defence architecture: the UK's military reach, intelligence depth, and diplomatic bandwidth were load-bearing elements that Brussels has not replaced. Any re-engagement on security is therefore not a concession — it fills a genuine capability deficit.

The Opinion Shift

The political ground beneath this discussion has moved significantly. John Curtice's June 2026 analysis for UK in a Changing Europe — published on 8 June 2026 — tracks a decade of public opinion and finds a growing majority now regard the Leave vote as the wrong decision. That shift is generational as well as directional: a majority of Gen Z in Britain believes Brexit has failed, with substantial support for a fresh referendum on EU membership. Polling data compiled by Statista corroborates the trend line, showing the share of Britons who regret Brexit has increased consistently since formal departure.

European publics, for their part, appear receptive. New ECFR polling published on 20 June 2026 finds that many EU voters view the UK positively — a finding that matters if any future government in Westminster decides to test the appetite for deeper re-engagement. Hostility to Britain within EU member states had been one of the quieter structural obstacles to any rapprochement; that obstacle looks less formidable than it did in 2020.

The Domestic Political Complication

Labour's positioning adds a layer of complexity. A BBC report from March 2026 noted that Labour's Brexit focus has shifted in ways that are raising concerns about the party's electoral standing with voters who backed Leave. That is the classic bind for any governing party trying to manage a re-engagement agenda: the public mood is moving toward regret, but the Leave-voter coalition is not monolithic, and alienating it carries real electoral cost, particularly in the English midlands and north where the 2019 and 2024 electoral maps were drawn.

The arithmetic here is worth holding. Curtice's data shows the shift in aggregate opinion, but aggregate opinion and swing-constituency opinion are not the same thing. A government that moves on EU relations faster than its political coalition can absorb risks the same structural punishment that Conservatives faced when they failed to deliver on the expectations Brexit raised in the other direction.

What Barnier's Appearance Signals

Barnier's presence at Chatham House is not incidental. He remains one of the few figures with personal credibility in both Brussels and London, having navigated four years of the most technically complex bilateral negotiation the EU has conducted. His renewed visibility on this question — and his reiteration that security should not be traded against market access — suggests an interest in shaping the terms under which any future conversation takes place.

The sequencing question is the hardest one. The EU's standard position has been that closer trade access requires regulatory alignment; London has resisted framing any re-engagement as alignment-by-stealth. Barnier's insistence on separating security from commercial leverage, if accepted by both sides, could provide one practical off-ramp: a UK-EU security and defence compact pursued independently of Single Market questions. That approach would deliver tangible value to Brussels — filling the capability gap the ISS identified — while allowing Westminster to avoid the politically toxic framing of 'rejoining' anything.

Whether the current Labour government is willing or able to move in that direction before the next UK general election is, at this point, an open question. What the past month's data — Curtice's polling, the ECFR findings, Barnier's Chatham House remarks — collectively establish is that the window for re-engagement is structurally wider than it has been at any point since 2016. The political will to climb through it is a separate matter.