Tall metal mesh barricades and concrete blocks have been erected around the perimeter of the US Ambassador's central London residence, Winfield House, where Trump will spend Thursday night.
A sign attached to the fence reads: "No access -- do not enter. A police security operation is taking place. This includes armed patrols, dog patrols, monitored CCTV and other measures." Any contravention, it warns, "could result in force being used against you, your arrest and/or prosecution."
The extra security measures may strike Londoners as incongruous, set amid the leafy surrounds of Regent's Park, a spot popular with joggers, picnickers and families.
"Yes, there might be protests," he said. "But I believe the people in the UK, Scotland, Ireland -- as you know I have property in Ireland, I have property all over -- I think that those people, they like me a lot and they agree with me on immigration."
But many disagree. On Thursday evening, protestors in in London had gathered in Regent's Park.
"He says we like him here but we don't," Roger McKay told CNN as the demonstration was taking off. "I haven't met anyone who likes him here."
McKay, who was carrying a sign that said, "Where do I start," said he was protesting for change.
"Trump is an opportunistic man who blames the world's problem on immigrants and vulnerable people. I grew up thinking the world gets better but this man embodies the opposite," McKay said.
By early evening, a few hundred protestors had mobilized inside Regent's Park, where they blared bells and whistles, chanting "Stay out, stay clear, Donald Trump get out of here."
Lewis Nielson was handing out posters that read: "Stand up to racism" and "Dump Trump."
The 25-year-old Londoner called Trump a "racist, sexist and bigot" and said the UK should not be spending millions of pounds on his visit.
"He gives confidence to racists around the world and here in Britain we have seen a rise in racism. Welcoming Trump endorses what he represents," Nielson said.
Trump 'not avoiding anything'
Earlier in the day, the President and First Lady Melania Trump landed at London Stansted Airport, northeast of the capital, where they boarded a helicopter to Winfield House.
The US Ambassador to London, Woody Johnson, insisted last week that Trump's itinerary was not intentionally designed for him to avoid encountering throngs of protesters.
"The President is not avoiding anything," he said. "The President is merely trying to get as impactful a trip as he can get in a 24-hour period."
Johnson added that the President "appreciates free speech" and that he was "very focused on the special relationship" between the US and the UK.
Trump may not be able to ignore the presence of protesters entirely. Some plan to stage an "all-night noise protest" outside the barricades surrounding Winfield House later Thursday, with those attending urged to "bring pots, drums and vuvuzelas."
Trump may 'double down'
On Friday, Trump will bypass the mass protests in London as he heads to the Royal Military Academy Sandhurst with May for a military display, before talks at her country residence, Chequers. Trump and the first lady will then have tea with Queen Elizabeth II at Windsor Castle in the afternoon.
However, media coverage may well be dominated by footage of the "Trump baby" balloon as it soars above the iconic Houses of Parliament for a two-hour spell.
Sarah Elliott, chairwoman of Republicans Overseas UK, told CNN she did not think Trump would be fazed by the stunt.
"I think whenever his detractors go after him, it makes him double down and it actually encourages him to keep going and prove everybody wrong," she said. "So I think that's the effect the balloon will have."
Blimp organizer Leo Murray said it had been designed to speak to Trump "in a language that he understands, which is personal insults."
But, he added: "Whether he sees it, whether he reacts to it, we don't really care. It's about lifting the spirits of the nation and it's already doing that, you know, it's just putting smiles on the faces of people who had started to despair about the state of politics."
Potentially tens of thousands are expected to march to a rally in Trafalgar Square on Friday afternoon, organized by the "Stop Trump Coalition."
Dozens of other, smaller protests against Trump's visit are set to take place around the United Kingdom throughout his stay.
On Saturday, Trump supporters will rally near the US embassy in Nine Elms, south London, for an event titled "Welcoming Trump to Britain Rally -- Make Britain Great Again," at which a number of right-wing figures are scheduled to speak.
The Trumps will have left town the night before for Scotland, where the President owns two golf properties, Trump Turnberry and Trump Aberdeen.
CNN's Erin McLaughlin contributed to this report.
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Donald Trump walled off from protests on UK visit