For three years, Brexit arguments have, naturally enough, focused on the impact that leaving the European Union might have on Britain. Less attention has been paid to the effect of Britain’s departure on the rest of Europe. That is about to change. The response of European neighbours to choices forced on them by the UK is getting harder to ignore.

A long article 50 extension would cover a turbulent phase in the European political cycle: European parliament elections; the appointment of a new commission; budget negotiations; the expiry of Donald Tusk’s term as council president. There is no precedent to indicate whether an exiting member can or should participate in those processes.

EU summits have always been conducted on the assumption that everyone wants a collegiate outcome. There is still disagreement, deadlock and strife, but they are contained by a framework of common enterprise. That is no longer true with Brexit Britain, which is why other European leaders, led by the French president, Emmanuel Macron, want to curtail UK privileges as the price of an article 50 extension.

It is not easy to sustain trust between a bloc of 27 EU members and a former ally loitering at the exit. It is much harder when the ruling party of the exiting country is a wellspring of anti-Brussels venom and when its MPs threaten to use their ongoing access to EU institutions for obstruction and vandalism. The breakdown in confidence works two ways. British ministers worry that any downgrade in status will be exploited to write anti-UK bias into the rules of future engagement across the Channel. But that is an intrinsic hazard of Brexit. There is no avoiding the diminution of influence that comes from surrendering a seat in the continent’s decision-making forums.

The leave campaign denied it was so. Brexiters promised that Britain would be the stronger side in negotiations with the rest of Europe; that they needed us more than we needed them. It is true that Theresa May had cards to play: British economic clout and military and intelligence capabilities are assets that the EU would rather not lose. But that leverage had to be exercised delicately. The shrewd way would have been to signal moral and strategic support for the European project, develop diplomatic goodwill and then use British assets to purchase influence for the long term. But the opposite happened. Brexit came across as an aggressive project, culturally aligned to Donald Trump’s anti-Europeanism, which provoked an impulse in Brussels to minimise British influence. That wasn’t Mrs May’s intention, but she allowed virulent anti-EU nationalism to run wild in her party.

EU leaders are frustrated with Britain, but they also recognise the necessity of maintaining healthy relations. The impulse to be rid of a nuisance neighbour is balanced by the calculation that an alienated, vindictive Britain poses more long-term threats. Sadly, the same equation is poorly understood in this country. Brexiters itch to escape EU institutional entanglements, but the country can never achieve pristine separation from the European project. Managing partnerships with our continental neighbours is an immovable fact of geography, diplomacy and economics. One approach to Brexit delay would be to reset those partnerships in a more constructive spirit. Another is to make them as difficult and dysfunctional as possible. It is clear which is the wiser path, but sadly also clear that Mrs May and her party are incapable of following it.