While Trump on Friday is having lunch with Prime Minister Theresa May at her Chequers country estate or sipping tea with Queen Elizabeth II at Windsor Castle, tens of thousands of demonstrators - maybe more - are planning to gather in London's Trafalgar Square to protest the president and his policies. Mr Trump is hardly likely to catch a glimpse of the six metre giant orange inflatable blimp that depicts him as a screaming baby.
The "Demonstration Alert" issued by the embassy also tells Americans to "exercise caution if unexpectedly in the vicinity of large gatherings that may become violent".
As well as in London, protests are expected to take place in Bristol, Newcastle, Leeds, Cambridge and Cardiff after Trump arrives on Thursday.
The couple will attend a black-tie dinner on Thursday at Blenheim Palace in Oxfordshire.
According to the Mirror, the US Embassy urged its citizens to remain vigilant during Trump's two-day visit beginning July 12, instructing Americans to "be aware of your surroundings" and watch local news for updates as the Commander-in-Chief tours the country.
As well as protests in London, a rally will be held on the steps of City Hall on Friday.
After his royal appointment, the president and Mrs Trump will travel on to Scotland.
U.S. Ambassador Woody Johnson said Wednesday citizens are often advised to avoid public demonstrations and that he is not upset by the decision to allow the "Trump baby" balloon to be displayed near Parliament.
It is not simply the protesters, who are expected to dog Trump throughout his visit, including his weekend in Scotland, but his fraught relationship with political leaders accustomed to harmonious exchanges with USA leaders, a tradition of unity that goes back at least to the vital World War II partnership of Franklin D. Roosevelt and Winston Churchill.
He also refused to endorse Ms May as prime minister and heaped praise on his "friend" Boris Johnson a day after he quit as foreign secretary.
Gardner, who works with refugees as part of her doctoral research at the London School of Economics, said Trump's speeches about refugees and immigrants are "a very unsafe line of rhetoric to be normalized".
Mr Trump will spend the weekend in Scotland where he has two golf courses and plans to play at least once.
"It's a disastrous and divisive time, and Trump is very much part of that", he said.
US President Donald Trump's visit to the United Kingdom will be an opportunity to boost trade links and strengthen cooperation on security, Theresa May has said.
Then on Monday, he will be off to Helsinki to meet with Russian President Vladimir Putin.