The resignation of Sir Kim Darroch proves a few things about the state of the United Kingdom as it edges towards Brexit. Only one is encouraging.

First, Sir Kim’s decision to put country before career shows that there is, in some parts of British life, still such a thing as a sense of honour. After Boris Johnson’s failed to back him in the latest ITV debate he must have realised his position was hopeless; Jeremy Hunt’s robust defence of him is of little use if Hunt doesn’t become PM, as he almost certainly will not.

What, by the way, if it was Johnson who leaked the emails? Although the PM-in-waiting has distanced himself from it. Or leaked them to someone who then leaked them to Isabel Oakeshott, the journalist? The Leave/Brexit Party nexus, pulling in the likes of Nigel Farage and Arron Banks, may be tighter than we imagine.

Ever the professional, with an excellent reputation from all who dealt with him, Sir Kim clearly decided that he was “becoming the story”, and that had made his departure inevitable – because the damage it was doing to Britain’s interests.

Hence his brave move. It is more than regrettable. Donald Trump’s behaviour is beneath contempt. Perhaps the foreign secretary, Jeremy Hunt, can relay that sentiment to the US ambassador to the UK, Robert Woods?

Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Show all 30 1 /30 Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Members of the Proud Boys, a fascist group, jeer at anti-Trump protesters outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter dressed as Uncle Sam poses at Uncle Sam Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A baby blimp rears its head amidst a group of anti-Trump protesters outside the president't campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam President Trump addresses supporters at the launch event of his 2020 election campaign in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Proud Boys have adopted Fred Perry polo shirts as their uniform and many members have the name of the group tattooed on their arms Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A line of police officers separate opposing groups of protesters outside the launch of President Trump's 2020 campaign launch Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A protester hits a Trump punching bag during a protest outside Trump's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Twin Trump supporters pose for a photo at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A protester dressed as a caricature of Donald Trump stands outside the president's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Trump supporter faces off against a protester outside the president's campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Proud Boy shouts across the police line at anti-Trump protesters outside the president's campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Trump supporter poses for a photo at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Proud Boy jeers at anti-Trump protesters who are separated from the president's supporters by a police line outside the president's campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A man dressed as Uncle Sam poses at President Trump's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester faces off against a supporter outside the president's campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Members of the Proud Boys, a fascist group, jeer at anti-Trump protesters outside of the president's 2020 campaign launch Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A child holds a 2020 US "dollar bill" that features Donald Trump's face at the president's 2020 campaign launch EPA Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Anti-Trump protesters rally outside the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Anti-Trump protesters rally outside the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Numerous baby Trump balloons are raised in protests outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter wears a T-shirt depicting Trump as a hero at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam President Trump addresses supporters at the launch event of his 2020 election campaign in the Amway Centre in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester calls for the president to be impeached outside the launch event for his 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Supporters of Donald Trump face off against protesters outside of the president's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A baby blimp rises behind a group of anti-Trump protesters outside the president's campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter dressed as Uncle Sam poses at President Trump's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A member of the Proud Boys, a fascist group, holds a sign up outside of the president's 2020 campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter bears a Trump flag at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Protesters hold baby Trump balloons in the rally outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester holds a sign accusing the president of being a traitor Getty

It would be satisfying if Hunt was able to tell him exactly what we think of Trump – wacky and very stupid in fact. Maybe some mysterious clash of diaries meant that Woods’ invitations to Buckingham Palace suddenly were to dry up. For good measure, Mr Hunt could add how much the British people regret ever having that buffoon Trump over for a state visits.

Sir Kim’s humiliation and resignation, by the way, makes it doubly important that the source of the leak is discovered.

The damage is done. Today, what ambassador or high commissioner is not going to hesitate before sending opinions back to London? Now more than ever, electronic communications are prone to hacking and leaks and this high-profile episode will have a chilling effect on the way our diplomats conduct their business.

At a time when the civil service and diplomatic service are increasingly demoralised, suffering a brain drain and being pummelled by political attacks by paranoiac Brexiteers as traitors, Brexit betrayers – Olly Robbins, chief Brexit agitator, being the prime example – we have to resist the politicisation of the civil and foreign services. It is openly talked of now that the cabinet secretary himself, Sir Mark Sedwill, will be pushed out of his job. And look at the carelessness with which secrets about Huawei were tossed out to the nearest hack, apparently by Gavin Williams, the defence secretary himself (although he has denied it).

These are depressing, dangerous developments. There is a huge turnover in the civil service and that is a very unhealthy sign: underpaid, undervalued, under-defended – no wonder they’re clearing off.

When Farage suggests that a “retired businessman” should be given the job, we know only too well what is going on. Some Brexiteer, in other words, if not Farage himself. A disaster. They would be telling their foreign masters and their chiefs back in London only what they wished to hear.

(In the 1930s, that was how the Foreign Office ran the embassy in Berlin – making sure that only pro-appeasement messages sympathetic to Hitler reached Neville Chamberlain and his cronies in Number 10. We know how that turned out.)

A healthy democracy needs checks and balances on the exercise of power by the executive, such as Parliament, the devolved administrations, the diplomats, the civil service, the Bank of England, business, civil society and the rest. Day by day these are being eroded.

The other thing the Darroch affair shows is that the UK is becoming diplomatically exposed and isolated as it moves away from the European Union, with its huge diplomatic and economic clout. Around 10 times bigger than us by GDP, the likes of the EU, the US and China do not really need to take much notice of any threats that the (relatively) tiny UK tries to make. They will always pursue their own interests, and owe the British nothing. It they want to throw their weight around, up to and including the bullying of an ambassador, then it seems there is little the UK can do to resist it.

“Global Britain” is a bit of a weakling when it can’t even name and retain its own representatives abroad, isn’t it? The debacle of Liam Fox’s aborted trade talks in Washington about sums it up

Support free-thinking journalism and attend Independent events

Who will succeed Sir Kim? You would hope that Hunt and Theresa May would appoint a permanent replacement, a professional who will try and do the job properly before Johnson gets his hands on the shortlisting. If not, then we can look forward to some Farage/Johnson puppet turning up. Richard Tice, Arron Banks, or – can you imagine – Ann Widdecombe maybe.

Or Farage, despite his flimsy denials about wanting the job. He would then soon discover how far his blokey bonhomie and banter about Churchill gets him with Trump. When it comes to the hard decisions on the US-UK trade deal, the British will get less than we get from the EU today – far less market access. As Sir Kim predicts, it will be an “America First” deal.

So. We’ve lost Sir Kim and a good slice of our national pride. In return we’ll be getting those gold ol’ American chlorinated chickens for dinner, and we’ll have to swallow a lot more besides, like US access to NHS contracts.