This bizarre, personal spat with our closest ally began yesterday when Donald Trump declared a de facto persona non grata status for Kim Darroch on Twitter. The British ambassador to the US had offered his professional observations of Trump and the administration in confidential memos to Theresa May, which then got leaked to the media. The outgoing prime minister noted — rightly — that Darroch was doing his job with those memos, although they have promised to open an investigation into the embarrassing leak of the memos.

That wasn’t good enough for Trump, who went on the Twitter warpath again this morning:

It’s worth noting that Darroch has served as ambassador to the US for more than three years, first starting almost exactly a year before Trump’s inauguration. Given the close nature of the relationship between the UK and the US, it seems rather remarkable that Trump has yet to even meet with Darroch. It’s just as remarkable to call someone “a very stupid guy” and a “pompous fool” in the same paragraph as an admission like “I don’t know the Ambassador.” Wouldn’t it be a good idea to meet the British ambassador first before coming to those conclusions?

Trump made sure that one recent opportunity to do so went nowhere. Darroch got “uninvited” from a dinner Trump attended last night, CBS News reports, and the US is increasing pressure on May’s government to make a change:

Even this is pointless, or perhaps even worse. May is only a caretaker PM now, waiting for Tories to pick a new PM before leaving the office. She doesn’t have enough political juice to make any significant changes. Furthermore, Trump’s public tantrum may make it even more difficult for May’s replacement to act. British career diplomats won’t take kindly to the personal attacks Darroch is enduring and will put plenty of pressure on the next PM not to incentivize such attacks in the future, even if some of them agree with Trump’s assessment of May’s performance on Brexit. This is just making it tougher on either Boris Johnson or Jeremy Hunt to replace Darroch when the time comes, and it will certainly mean that the next envoy won’t be Nigel Farage or anyone of his temperament.

It’s tough to see the upside for Trump, too. Right now he needs the UK to help rally the rest of our European allies to keep Iran isolated, which matters a lot more than Darroch’s privately expressed opinions about Trump. The Brits have been somewhat more sympathetic to our arguments on Iran than some other European leaders angry over Trump’s reversal on the JCPOA. This only erodes the diplomatic cohesion necessary to generate a reluctant unity against Tehran.

The only possible point there might be to this nasty feud with a diplomat of our closest ally is as a distraction from something else. Even that possibility sounds ominous, as it’s tough to envision any positive development worth distracting from to achieve as to justify this diplomatic rift.