One of the many imponderables in the post-Brexit world is the way in which Britain’s key bilateral relationships with its erstwhile European partners is likely to change. In the short run all these relationships will be affected by arm-wrestling over the terms of disengagement. In the long run, the UK will continue to have to weigh carefully its diplomacy towards Germany, as the EU’s leading power. But there is also the critical and delicate question of the London-Paris axis, which has been central to Europe’s foreign policy-making for the last four decades, and which is institutionalised through the Lancaster House Treaties of 2010. Will this close, but difficult, relationship be dismantled by the UK’s departure from the EU? It seems hardly in either state’s interests that it should be.

The two countries have many obvious things in common: alliances in two world wars; the need to manage relative decline; permanent membership of the UN Security Council; nuclear deterrents; the capacity to project conventional force beyond Europe (within limits); ambivalent relations with ex-colonies, and more. But none of this has produced the kind of solidarity which exists between Paris and Berlin. Britain and France maintain an uneasy entente which can quickly break down under pressure – as over Iraq in 2003. In particular their approaches to European integration have been sharply different, with the UK acting as a force for stasis and France committed, at least in principle, to ‘ever closer union’. The British referendum this year has brutally exposed this difference and calls into question the ability of the two states to remain in harness as the leaders of Europe’s foreign policy-making process. France might simply despair of British reliability, whether in multilateral or bilateral forms of cooperation.

Yet despite the obvious reasons to assume increased divergence – including the neuralgia of the British tabloids over the prospect of a ‘European army’ – there are good reasons to think that France and the UK are doomed to work together in foreign and security policy. For one thing no British government could commit itself simply to following the US lead in world affairs – let alone that of a Trump presidency. The ‘poodle’ stereotype is already prevalent in anti-western circles and it does the UK no favours in politics or in trade with the wider world. Yet London has nowhere else to go if it has to cut itself loose from the CFSP system in which it has had a leading role for 46 years, and which  indeed was the only part of the EU project where Britain was ‘present at the creation’. Pure unilateralism adds up to very little for a country struggling to find the resources to sustain its welfare state, and with a population one twentieth the size of India’s. By the same token the rising powers are unlikely to want ‘strategic partnerships’ with an ex-imperial country whose need for trade and investment is greater than theirs – as we saw with Theresa May’s fruitless recent visit to India. Thus Britain has a strong interest in staying in the European foreign policy club.

It does not follow that the other 27 will allow this to happen, though most observers assume that the ability to offer diplomatic, security and counter-terrorist cooperation is one of the strongest cards in London’s hand as it negotiates Brexit. But France in particular will be reluctant to watch the UK float away into the distance from the rickety European armada. It is true that in terms of defence cooperation form is more prominent than content. The main framework here is NATO, where France has become increasingly comfortable and Britain has a key role.  In relation to nuclear weapons the two states manage some discreet cooperation but have no intention of creating the joint force that Edward Heath dreamed about in the 1970s. On defence industries and arms sales they are serious competitors, for all the regular talk of combining expertise. Even inter-operability is a distant prospect.

Yet foreign policy is different. The need of each country not to be isolated on major political issues like the Middle East, non-proliferation, and the stability of fragile regimes in sub-Saharan Africa, is a powerful driver of cooperation. Iraq has had the effect of making both London and Paris understand better the need for solidarity, evident over Libya, Mali, Russia and (after a hiccup) Syria.  The dual fear, of isolation on the one hand and of US volatility on the other, is likely to keep the two in close diplomatic touch even after Brexit, and could therefore in practice give the British an informal seat at the CFSP table.

This may seem like wishful thinking. There are plenty of difficulties in Franco-British relations even without the Brexit negotiations. The Treaty of Le Touquet, which has allowed the UK to avoid migrant pressures at Dover, might well be renounced by President Hollande’s successor. The two countries have very different approaches to multiculturality and to policing, which has led in the past to serious problems over extradition. If pushed Paris will always choose Berlin over London, given the continued importance of the Elysée Treaty and the joint role of France and Germany at the heart of the EU. What is more, if Britain’s departure does finally spur Germany on to punch its weight in foreign and security policy then France will have far less need of a partnership with Britain.

Still, this last scenario remains unlikely for the foreseeable future, in which case Paris and London have few incentives to fall out on foreign policy, even allowing for the difficult bargaining ahead over Brexit.  History, geography and similar positions in the hierarchy of international politics, make for a natural alliance, if not for the fusion envisaged in Churchill’s proposal of 1940 in   desperate circumstances.  Yet this view derives from the assumption that both countries do still pretend to play significant foreign and security roles in world politics. Certainly neither state could envisage taking on by itself a military intervention of the kind they carried out together in Libya during 2011. Neither wishes to risk losing its permanent membership of UNSC, and by the same token, each needs the help of the other in order maximise its weight on the major issues in that forum – not least to defend the right of middle range European states to possess nuclear weapons.

If either France or the UK were to turn inwards and to turn away from centuries of activism, then the parameters of the problem would change radically. But it is difficult to imagine their foreign policy establishments settling for a role like that of Sweden, or even Italy. If Donald Trump wants to move the United States towards insularity he will have some big internal battles to fight and the same would be true in Whitehall and in Paris. The two countries might be divided on many issues, but they share an aspiration to be seen as Europe’s leading foreign policy players, and to continue on their historical paths of deep engagement in international politics. In that context Brexit might be seen as little more than a blip.

Further Reading on E-International Relations

• Anglo-French Defence Relations are Crucial for European Defence after Brexit
• An ‘Expert’ Perspective on Brexit… Means Brexit
• Brexit and the Consequences for International Peacebuilding
• The UK’s Global Role Post-Brexit: What is Worth Researching?
• Lingering Effects of the UK’s Brexit Role Change
• The Days of May (Again): What Happens to Brexit Now?