Starmer resets UK-EU ties with defence, nuclear and migration deals

Keir Starmer's Labour government has managed in roughly two months what fourteen years of Conservative administrations could not: a substantive, multi-layered reset of the United Kingdom's relationship with the European Union and its largest member states. Since the Prime Minister took office in July 2024, London has signed a broad bilateral treaty with Brussels, a nuclear coordination agreement with France, a mutual defence pact with Germany, and a pilot migration returns deal with Paris. The speed is striking, but the constraints are equally deliberate.

Geopolitics forces the pace

The catalyst is not a sudden outbreak of Europhilia in Westminster. It is the war in Ukraine, the persistent threat from Vladimir Putin's Russia, and the prospect of a United States under Donald Trump that treats European security as an optional extra. Those three factors have concentrated minds in London, Paris, Berlin and Brussels alike. The EU's own rearmament plans, accelerated by Washington's wavering commitment, created a moment where British military-industrial capacity and diplomatic weight became too valuable to keep at arm's length.

As Joël Reland of the UK in a Changing Europe think tank puts it, strategic interdependence has intensified with the US withdrawal from a rules-based world order. The UK remains, alongside France and increasingly Germany, a central power on NATO's European flank. That reality made a defence-first reset the path of least political resistance for a Labour government that campaigned on repairing Brexit damage but drew hard red lines: no rejoining the EU, no single market membership, no customs union, no restoration of free movement.

The EU-UK treaty: defence, fisheries, customs, youth

The centrepiece arrived on 19 May 2025 when Ursula von der Leyen travelled to London to sign the first formal bilateral treaty between the EU and the UK since the Trade and Cooperation Agreement entered force in 2021. The text covers joint financing of rearmament, shared industrial planning, a common security strategy, fisheries access, customs cooperation and a youth mobility scheme. Von der Leyen described a strong EU-UK relationship as fundamental to European security, prosperity and shared destiny. The language was warm; the substance was practical.

Fisheries was always the most politically toxic file for any UK government. The treaty does not restore the pre-Brexit quota shares but establishes a framework for annual negotiations and scientific cooperation that both sides hope will depoliticise the issue. Customs cooperation focuses on trusted trader schemes and data sharing to reduce friction at the border, a tacit admission that the current arrangements impose costs neither side can afford. The youth mobility scheme, limited in scope and duration, is a concession to universities and creative industries that have lost easy access to European talent.

Northwood Declaration: France drops a nuclear taboo

If the EU treaty was expected, the Northwood Declaration was not. During a state visit by Emmanuel Macron, complete with the ceremonial pomp the British monarchy deploys so effectively, the two NATO nuclear powers agreed to coordinate their deterrent capabilities. France has guarded its nuclear autonomy jealously since Charles de Gaulle; the Force de frappe was built precisely to avoid dependence on Washington or London. That Paris now accepts explicit coordination with the UK marks a strategic shift driven by the same geopolitical pressures.

The declaration, named after the Northwood military base where the leaders met, stops short of joint targeting or shared command. It establishes a framework for regular strategic dialogue, joint exercises and information exchange on submarine patrols and missile maintenance. For the UK, which relies on US-supplied Trident missiles for its deterrent, French partnership offers a European hedge. For France, British submarines and the Clyde base add depth to a deterrent that has always been national in doctrine but increasingly European in necessity.

Migration: a pilot returns scheme with Paris

Alongside the nuclear agreement, London and Paris launched a pilot project allowing the UK to return some irregular migrants who cross the Channel to France. The numbers are small and the scheme is explicitly time-limited, but the principle matters. Since the UK left the EU, it lost access to the Dublin Regulation that determined which member state was responsible for an asylum claim. France had consistently refused bilateral returns, arguing that the UK's departure ended reciprocal obligations. The pilot suggests that calculus has shifted, at least at the margins.

Home Office officials describe the scheme as operational rather than political: a test of whether French reception capacity and UK casework timelines can align. Critics note that the vast majority of Channel arrivals come from countries, Afghanistan, Iran, Syria, Eritrea, that France cannot easily return them to either. The deal does not address the root causes of the crossings, but it gives both governments a mechanism to claim progress before their respective electorates.

Kensington Treaty: Germany adds a bilateral layer

In mid-July 2025, Friedrich Merz signed the Kensington Treaty with Starmer. The text obliges each country to assist the other, including by military means, in the event of an armed attack. NATO's Article 5 already covers this, but Berlin and London wanted a bilateral reinforcement that survives any future ambiguity about US commitment. The treaty also secures easier movement for students and professionals, a German priority given labour shortages in engineering, healthcare and IT.

Merz, who took office in 2025 after Olaf Scholz's coalition collapsed, has made European defence autonomy a signature issue. The Kensington Treaty fits his narrative of a Germany that leads rather than waits. For Starmer, it is further evidence that the reset extends beyond Brussels to the capitals that matter most. The symbolism of a British Prime Minister and a German Chancellor signing a mutual defence pact in Kensington Palace would have been unimaginable five years ago.

Public opinion has moved, but red lines hold

Hugo Dixon, founder of Breakingviews and a veteran of the Remain campaign, cites YouGov polling showing that only 30% of Britons now think leaving the EU was the right decision, while nearly two-thirds want a closer relationship and 55% would like to rejoin. Those numbers have shifted steadily since 2020. Yet Starmer's government treats them as a ceiling, not a mandate. The red lines, no single market, no customs union, no free movement, are enforced as much against Labour's own backbenchers as against the Conservative opposition.

The political calculation is clear. Any move that looks like Brexit reversal would reignite the culture war that dominated British politics for a decade. Starmer's majority is large but his coalition is fragile: Red Wall seats that voted Leave in 2016 sit alongside metropolitan remainers. The reset is designed to deliver tangible benefits, defence contracts, border cooperation, research funding, without triggering the identity politics that Brexit unleashed.

Financial services: the unresolved competition

Joël Reland notes that financial services may be the only area where the UK and EU remain more competitors than partners. The EU has not granted equivalence determinations that would allow frictionless access for UK-based banks, asset managers and insurers. The UK, in turn, has diverged on some regulatory standards, most notably the Senior Managers and Certification Regime and the Edinburgh Reforms, to signal independence. A memorandum of understanding on regulatory cooperation exists but has not produced the market access the City expected.

This matters because financial services account for roughly 7% of UK GDP and a larger share of tax receipts. The EU's capital markets union remains incomplete, and both sides benefit from London's depth. But the political trust required for equivalence, a unilateral EU decision that can be withdrawn at thirty days' notice, has not returned. Until it does, the reset has a significant hole in its commercial centre.