Another day, another troubling development in UK/ EU relations. Earlier this week, a British trawler was seized by France and another fined. Now, France’s prime minister has written to the EU asking for its backing for further measures against the UK because of the refusal of various fishing licenses. The letter asks for support because, Jean Castex says, it must be demonstrated that ‘leaving the Union is more damaging than remaining in it.’

The UK, for its part, has summoned the French ambassador over the issue. Britain has made it clear it will carry out ‘rigorous enforcement processes’ on EU vessels fishing in UK waters if the French carry through on their threats. It has also suggested it could trigger dispute resolution proceedings under the UK/EU free trade deal.

But it isn’t only fishing which is causing tensions. On the Northern Ireland protocol, the Commission has made it clear to member states that the role of the European Court of Justice is not up for discussion in these talks. This makes it hard to see how what the UK calls ‘substantial’ gaps can be closed following today’s meeting between Lord Frost and EU Commission vice president Šefčovič. (Oddly, a British readout of Boris Johnson’s call with the Polish PM drew a link between the ECJ issue in Northern Ireland and the situation in Poland. Why the UK would want to do that is unclear given the Poland issue is one of the reasons why the EU is so determined not to move on the ECJ’s role on the protocol).

All this points to a further deterioration in UK/ EU relations. A UK triggering of Article 16, the emergency brake of the Northern Ireland protocol, would likely set off a series of events that would result in the EU imposing tariffs on some politically sensitive British goods. Once that has happened, it is all too easy to see how things turn into a full-blown trade war given the personalities involved and the fact that France is taking on the EU presidency in January.