It also helped that Mr. Macron saw off Marine Le Pen in the second round of the presidential election. France didn’t succumb to populism. Brexit Britain could only look on in envy, wondering what might have been. And now, many Britons see in Mr. Trump a reflection of the Brexit phenomenon, albeit a more orange and sordid one.

In preparation for his visit, some of our most hallowed institutions are being sealed off for fear that Mr. Trump will tarnish them with his presence. Plans are under wraps, but the president is not expected to have a meeting with the queen at Buckingham Palace, which is unusual. Instead, he is scheduled to meet Her Majesty behind closed doors at Windsor Castle. The Duchess of Sussex — or as the new American member of the royal family was known before her marriage to Prince Harry, Meghan Markle — has made it obvious that she does not like Mr. Trump. It is unclear yet whether she will grace him with her presence.

Mr. Trump is not expected to meet the prime minister at Downing Street but will dine with her at her country retreat, Chequers. He is expected to avoid much of London, a city which has become a bastion of both anti-Brexit and anti-Trump sentiment. Instead, he is likely to visit Blenheim Palace, the Oxfordshire birthplace of Winston Churchill, and then head to Scotland to visit his golf course.

The Stop Trump campaign says it intends to “shine a light on Trumpism” in Britain. It also claims it has never taken a position on Brexit. There is, of course, genuine disgust at many of the president’s policies. But Britain is also a country grappling with a lot of its own political anxieties at the moment and it seems fair to wonder if there is some projection going on.

Out of the hundred or so prominent signatories who have backed the Stop Trump campaign — a list that includes the pop star Lily Allen, the former Labour leader Ed Miliband and Mick Jagger’s ex-wife, Bianca — the overwhelming majority are pro-European Union. One gets the sense that the campaign’s members hope that if they can stop Mr. Trump — whatever that may mean — they can stop Brexit too. Or at the very least, they can unite the nation against the horror in the White House.

But just because the Stop Trump movement, like the Stop Brexit movement, shouts loudest, it doesn’t mean it speaks for the nation. Quite a lot of Britons, like quite a lot of Americans, don’t abhor Mr. Trump and everything he stands for. Many would rather welcome him if only because it makes diplomatic sense.

In February, a YouGov poll found that 45 percent of Britons supported a state visit by Mr. Trump, against 39 percent who opposed it. And not everybody is planning on protesting Mr. Trump’s arrival: in Oxfordshire, a barman has said he would happily welcome Mr. Trump in, shake his hand and serve him a free drink. If that happens, it would horrify the snobs, but it could turn out to be the most diplomatic gesture of the entire trip.