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.
Meanwhile, London Mayor Sadiq Khan has granted permission for a giant inflatable figure depicting Mr Trump as a baby to fly over Westminster for two hours on the second day of the president's visit.
Its advice to US citizens was to "keep a low profile" and "exercise caution if unexpectedly in the vicinity of large gatherings that may become violent".
President Trump will head to London on Friday, where he's expected to face protests at every turn.
The couple will attend a black-tie dinner on Thursday at Blenheim Palace in Oxfordshire.
Trump will spend Thursday night in London at Winfield House, the official residence of U.S. Ambassador to Britain Robert "Woody" Johnson.
The two leaders will hold talks the following day at Chequers, the 16th-century manor house which is the prime minister's official country residence which will focus on Russian Federation, trade, Brexit and Middle East.
"Numerous demonstrations are being planned for July 12 to 14, 2018, surrounding the visit of the President of the United States to the United Kingdom", the embassy's website states.
Protests are also planned in more than 30 towns and cities around the country, including Cambridge, Cardiff, Edinburgh and Belfast.
Mass protests are expected across Britain, leading police to mobilize to a degree not seen since 2011.
Mr Trump is the 12th sitting USA president to make such a trip and will spend time with the Queen and prime minister before flying to Scotland to spend the weekend at his golf resort.
Mr Trump tweeted of his visit cancellation: "Reason I canceled my trip to London is that I am not a big fan of the Obama Administration having sold perhaps the best located and finest embassy in London for "peanuts", only to build a new one in an off location for 1.2 billion dollars".
Mr Smyth, who is originally from Ireland, said Trump fans had been given a bad rap, and there had been lots of support for the pub's temporary renaming.
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.
"He's been very, very nice to me, very supportive", he said.