Sand eels are not even eels. They are long, thin fish, useful to humans only to produce fishmeal. But puffins and kittiwakes love them; and in view of these birds’ declining numbers, the UK last year imposed a ban on sand-eel fishing in its waters. The EU objected: and the issue is now in the hands of international arbiters.

This sort of dispute is only too typical of the manifold frictions to which Brexit has inevitably given rise and which perpetuate cross-Channel mistrust. This is despite the more emollient language adopted by both sides since the Labour party came to power last July in the UK, in September calling for a reset in UK and EU relations. Prime minister Keir Starmer’s main idea behind this was for a new security pact, although progress has so far not been evident.

But US president Donald Trump has, in two short months, demolished the assumptions on which European security has rested since world war two. Now restoring the closest possible defence and security relationship between Britain and its continental neighbours should be an overwhelming priority for both sides.

Certainly, the last few weeks have seen an unprecedented slew of initiatives. The EU and European capitals are all aiming to enable Europe to defend itself even if Trump abandons not only Ukraine but his NATO allies as well. Perhaps most startling has been the frugal Germans’ decision to amend their constitution to permit hundreds of billions of euros of new borrowing for defence and other investment. In parallel, the EU has decided to relax its own fiscal rules to allow member states to incur more debt for security and defence spending, while the commission will raise €150bn against the common EU budget to finance collaborative equipment procurement by member states.

The European Commission has also published a White Paper spelling out the key capability gaps which this money must plug (air defence, deep strike, drone warfare and other deficiencies highlighted by the Ukraine conflict). Even the once-taboo idea of Europeans organising their own nuclear deterrence has resurfaced.

Meanwhile, Britain has committed to increase its own defence budget to 2.5% of GDP by 2027, and is working with France to assemble a “coalition of the willing” ready to deploy joint forces in support of any ceasefire deal in Ukraine. While such a deal looks improbable, the main virtue of this initiative may be to accustom European military chiefs to work together on plans without the Americans to tell them what to do—in relation not only to Ukraine, but for Europe as a whole.

Against that background it was dispiriting to see signs of divergence and backsliding already appearing at the EU summit on 20th March. Hungary, of course, broke consensus on the political statement in support of Ukraine. Much more serious was the failure to agree urgent new military aid to Ukraine: the commission’s high representative, Kaja Kallas, proposed €40bn package which got nowhere. Not even a commitment to deliver €5bn of ammunition and missiles was agreed.

And Italy and Spain, Europe’s two principal under-performers against the current NATO 2%-of-GDP defence spending target, argued for a more relaxed interpretation of what increased national expenditure on “security” might comprise, embracing for example combating climate change. A fissure between north and south is already beginning to appear in the initially impressive European unity following the Trumpquake.

Never has Brexit looked more damaging, to both sides. Britain’s robust voice is badly missed in the EU’s inner counsels; and as Europeans seek to build their own capabilities free of dependencies on the US—Trump’s week-long suspension of intelligence and material support to Ukraine was an unmissable warning—the full involvement of Britain’s defence industrial base is precluded. Current EU-backed defence programmes such as the European Defence Fund are confined to EU member states (with one or two exceptions, notably Norway), and the new €150bn defence pot will similarly be directed at EU defence industries.

Given the imperative for all Europeans to build defence capabilities and technologies free of US control, this is understandable. Yet the task will be immeasurably harder for both Britain and EU member states if they cannot freely pool their efforts and resources—which makes it imperative that they agree a new UK/EU security and defence pact to bridge this mutually damaging divide. If the EU can make an exception for Norway, why not Britain as well? The answer is that Norway, though not an EU member, is inside the bloc’s single market. But devising a workable special status for the UK should be quite feasible.

Of course, Britain will have to bring its own money, either as a subscription to EU programmes, or on a pay-as-you-go basis for individual shared projects. And a fair deal will need to be struck on control of jointly developed technology, with implications for both commercial intellectual property and for security of supply.

The upcoming EU-UK summit on 19th May must focus minds. Europe’s geopolitical situation, as leaders across Europe have constantly averred in recent weeks, is now more perilous than at any time since the second world war. Delivering an EU-UK security and defence partnership at the summit would be an important symbol of Europe’s unity and determination, as well as a key practical advance.

Kallas has declared it doable, while also alluding to “worries” among EU member states. This, alas, is the renewed shadow of Brexit. The Trade and Cooperation Agreement is due for review next year; and already each side is compiling lists of what it would like to see changed, covering issues as diverse as youth mobility, veterinary checks, energy cooperation—and fishing quotas.

It will be a historic failure of statesmanship if the two sides allow such issues to contaminate the May summit, and derail the all-important security and defence pact. The EU and UK have bigger fish to fry than sand eels.