In a certain sense, I suppose you could say that Prince Harry, Meghan, King Charles, the late Queen and the entire British people got off lightly. When Donald Trump barrels in with his opinions on something that is nothing to do with him, like a drunk uncle who grabs the microphone at a wedding, they are generally the ill-informed, maladroit ramblings that might presage a full-scale diplomatic incident.

So when the President of the United States, sitting at a desk in the Oval Office, photographs of his family (and himself) behind him and flanked by his senior staff, loaded the verbal blunderbuss and began to fire off his views on the delicate subject of the British Royal Family, any amount of damage might have resulted. By now, however, we are so used to such impromptu interventions that we can be pretty sure that, within the House of Windsor, the latest Trumpian broadside will have been treated with studied insouciance.

It was not, it has to be said, an unsolicited opinion. He was asked by a reporter what his reaction was to the news that Prince Harry and Meghan had left the United States and gone back to Britain. “I’m happy about it,” was Trump’s (semi-playful) response. He was “not a fan” of the couple, he said, and, of Meghan, he added: “I didn’t like the way she acted. I thought she was terribly disrespectful to the Queen, [and] to King Charles.” Our King, on the other hand, is “a great guy”.

But it was his final assertion that was startling, and revealed much about Trump family values. “Maybe I’m different,” he said, “but I wouldn’t have taken them back. Frankly. If I were the Royal Family, I would not have taken them back.”

There is so much to unpack here, but what does he actually mean when he says they shouldn’t have been “taken back”? They are not returning to assume duties as royal personages. They are merely moving back to the country of Harry’s birth and, by all accounts and as much as is possible or practical, they will live as a private couple with their two children, and their dogs. The idea that, by royal decree, they should be turned away at the border says everything about Trump’s idea of the family as an organisation bound by rules, rather than governed by blood ties, privacy and complicated emotions.

Trump’s own family – five children by three wives, and 11 grandchildren – has always been central to his business and political life. His children have appeared alongside him at rallies, they have worked in his business empire and, in some cases, have become part of his political machine. His grandchildren, too, have become familiar figures in the Trump universe.

“The family is really the foundation of a prosperous and good society,” Trump has said, but his idea of family goes beyond the fundamental, interdependent social unit. It is more like a tribe, or a guild, with its own codes of behaviour to which all must adhere. And the most important rule of all is loyalty. This is why Harry and Meghan have offended him so much. He deemed them to be disloyal to the Crown – he’s not alone in that, to be fair – and believes they should be punished by ex-communication.

Trump doesn’t seem to understand that families are not like business organisations. You can’t fire a son. You can’t put a daughter-in-law on gardening leave. There are no contracts you can cancel. And you certainly can’t prescribe where they can and cannot go. This is why the King’s situation is a very delicate one. He must try to keep the family together, no matter what pressures – internal and external – are exerted.

This is the sort of nuanced position that is antithetical to Trump’s style of megaphone diplomacy, and thus far, the King has handled it well. He has not said anything in public, but is reportedly pleased at the prospect of seeing his son and grandchildren more often while being clear there will be no return to royal duties. And while Trump was sounding off in Washington, Charles was, on behalf of the nation, receiving the Bayeux Tapestry at the British Museum.

Princess Diana referred to the Royal Family as “The Firm” because she felt they acted in a cold, impersonal, strictly institutional way. King Charles, and Prince William, are trying present a more conciliatory, more human face to the world, and they don’t need Donald Trump’s advice on how to deal with the Harry and Meghan problem. They should merely treat it as another blast of hot air coming from across the Atlantic.