The trip coincides with a tumultuous week for May after two senior ministers resigned in protest..
While she hopes the Trump visit will focus on trade and strengthening security ties, it is likely to be heavy on rhetoric about the transatlantic "special relationship" and short on specifics such as any details of a post-Brexit trade deal. Protesters also have plans to follow Trump to Scotland where they plan to fly the blimp near Turnberry while Trump is in town. "With a lot of resignations", Trump told a news conference at the North Atlantic Treaty Organisation summit in Brussels. "The people voted to break it up so I imagine that is what they would do, but maybe they're taking a different route".
In an interview with Britain's Sun newspaper published late on Thursday, Trump said May's plans for a business-friendly Brexit would leave it too close to the European Union to allow a new trans-Atlantic trade deal to be struck.
That turmoil includes the resignations of May's Brexit and foreign ministers over her plan to retain close ties with the European Union after leaving the bloc in March.
Some Brexit supporters have cast May's Brexit plan as a betrayal, including MPs in her own deeply-divided party who have warned of a leadership challenge.
Trump has been quick to criticize British society, telling a National Rifle Association convention in May that the British didn't have guns but had so much knife crime that one hospital was like a military war zone with its floors awash with blood, a false statement quickly rebutted by British physicians and politicians.
Despite not being an official state visit, the Government is desperate to ensure the USA leader feels he is being treated with the appropriate level of pomp and ceremony.
Some 77 percent of Britons have an unfavorable view of Trump, according to a poll by YouGov with 1,648 respondents.
President Donald Trump says he used to like London a lot. "I think meeting with people is great".
"The United States commitment to North Atlantic Treaty Organisation is very strong", he said.
But trip planners may go out of their way to shield Trump from viewing another aspect of the greeting: an oversized balloon depicting the president as an angry baby in a diaper that will be flown from London's Parliament Square during what are expected to be massive gatherings of protesters opposed to Trump's presence.
"But from the public, the welcome will be far from warm", he added saying there would be protests across the country against Trump's "abysmal record on human rights, his repugnant attitude towards women and his disgusting treatment of minorities".
Trump and his wife, First Lady Melania, will land at London's Stanstead airport after attending a North Atlantic Treaty Organisation summit in Brussels.
A campaign is also underway to get "American Idiot", a 2004 song by the United States punk rock band Green Day, to the top of the UK Singles Chart.