Considering that the width of the Channel does not change, it is surprising how often British politicians seem surprised by the proximity of France. Currently, Priti Patel is enraged by the volume of people making the crossing in small boats. Boris Johnson is frustrated by Patel’s inability to stop the traffic. Tory MPs who told constituents that Brexit had secured the nation’s perimeter are alarmed to find that their boast was premature. Britain alone cannot deal with migrations that are launched from Calais. The home secretary and the prime minister tried blaming French authorities for slack policing, but then realised the folly of antagonising a government whose help they badly need. The problem is that borders have two sides and there are limits to what can be achieved by “taking back control” of just one of them. Also, Brexit ideologues were confused about water. They saw the ocean west of Britain as a maritime motorway for shipping goods and the much smaller sea on its south-eastern flank as a moat to keep out people. In 2018, Dominic Raab stunned a conference auditorium with the admission that he “hadn’t quite understood the full extent” of UK economic reliance on Dover-Calais trade. Managing EU frontiers post-Brexit was always bound to be tricky. It is harder when relations with Paris are tetchy. Migration is just one point of tension. Fisheries access is another. Emmanuel Macron was affronted by his country’s exclusion from the recent UK-Australian-US (Aukus) security partnership deal. Downing Street sees the French president as an enemy of Brexit who preaches Anglophobia in Brussels. It is true that Macron takes a hard line against anything that might undermine the single market or chip away at EU solidarity. That is because he recognises the European project as an amplifier of French power. Also, there is a presidential election next year in which the incumbent will face Eurosceptic challengers. He could do without a nuisance neighbour furnishing his rivals with positive anti-Brussels case studies. Ministers talk about Macron’s posturing for a domestic audience with patronising indulgence, as if it is a uniquely foreign practice unknown in straight-talking Britain. Downing Street is reported to be planning a grand rapprochement once next year’s Elysée poll is out of the way. There is talk of a deep strategic partnership, building on the Lancaster House agreement that David Cameron and Nicolas Sarkozy signed in 2010. That is a plausible ambition to the extent that western Europe’s two biggest military powers share long-term security interests that transcend any bickering over cod. Also, defence issues are primarily a nation-state concern, even for the most integrationist EU leaders. The Lancaster House treaties were signed between two EU members. Brexit does not undo the logic of that partnership, but Johnson’s government makes life harder for itself by pretending that its foreign policy with continental capitals and its trading relationship, as mediated through Brussels, are separate things and scarcely related. Lord Frost, Johnson’s Brexit minister, has been explicit on this point, describing a future relationship with the bloc as a patchwork of bilateral deals with member states. The foreign secretary, Liz Truss, does not appear to consider European relations part of her job at all (perhaps because Frost has bitten off that portion of the portfolio). Denigration of EU relevance is a requirement of belief in Brexit. To accept that Macron’s pro-EU stance reflects a rational appraisal of his nation’s interests risks admitting that an equivalent dynamic once applied on this side of the Channel. After all, the two countries have so much in common. But that was the remainer argument (albeit one that was poorly articulated in the campaign). So other reasons must be confected as to why relations with France have become so prickly. The leader of the House of Commons, Jacob Rees-Mogg, suggested that dialogue was uniquely tricky last month because “the French are always grumpy in October, the anniversaries of Trafalgar and Agincourt upset them”. Even if he was not being serious, it says something about the degradation of British political culture that seriousness is not a requirement when cabinet ministers intervene in delicate matters of foreign relations. No one on the French side has felt compelled to raise the Battle of Castillon. The childish compulsion to reference medieval wars, Napoleon and the Third Reich is a way for Brexiters to deny contemporary economic and strategic reality of the European project. There is no need to build an analysis from modern facts or even recent history if the EU’s immutable character and secret agenda are encrypted in events that pre-date the Treaty of Rome. The parochialism that masquerades as historical erudition is a chronic syndrome in Tory Euroscepticism. It is Johnson’s preferred idiom as a propagandist, not least because it excuses him from a duty to engage with detail. But it does not translate into practical government. It nurtures the fiction that Britain can have a foreign policy for old continental powers that avoids engaging with their modern interests as members of the EU. That is the core of the misunderstanding with France, and the relationship will not be fixed until it is resolved. The reality of 21st century Europe cannot be wished away any more than the Channel can be made wider.