May hopes Trump, who landed at Stansted airport before flying by helicopter to the US ambassador's London residence, will help to accelerate a future free trade deal, though his public comments on Brexit cast a shadow over the visit.
"There is no stronger alliance than that of our special relationship with the U.S. and there will be no alliance more important in the years ahead", the British leader said.
Trump and his wife, First Lady Melania, will land at London's Stanstead airport after attending a North Atlantic Treaty Organisation summit in Brussels.
"I just want the people to be happy".
Some 77 per cent of Britons have an unfavourable view of Trump, according to a poll by YouGov with 1,648 respondents. And I said Putin maybe the easiest of them all.More news: Elon Musk showed at Thai cave rescue despite his 'impractical' sub
Speaking about the protests - that includes a giant balloon baby flown over Parliament - Trump told reporters in Brussels that he was well-regarded by Brits.
The Stop Trump Coalition accused the president of being "too scared to face protestors".
In anticipation of the massive protests planned for President Donald Trump's visit to the United Kingdom on Thursday, the U.S. Embassy has warned Americans to "keep a low profile" in the English capital.
Rarely has a foreign leader been so mocked on an official visit - London's mayor, Sadiq Khan, a Muslim who has challenged Trump's worldview OK'd the balloon, which is an apt symbol of Trump's tempestuous relationship with Britain, traditionally the United States' closest ally.
Meanwhile, in the capital city thousands will gather in a various of protests to voice their views against the USA president, including a march that could be attended by as many as 50,000 people and a flying protest involving the "Baby Trump" balloon. "I like Boris Johnson, I've always liked him", said Mr Trump.More news: President Trump declares North Atlantic Treaty Organisation a 'fine-tuned machine' at conclusion of summit
A campaign is also underway to get "American Idiot", a 2004 song by the USA punk rock band Green Day, to the top of the UK Singles Chart.
For Trump, there has been no such tension with Churchill, who is revered by American conservatives for his stalwart leadership of Great Britain during World War II and his role in defeating the Nazis.
He will spend just one night in the capital before going to Prime Minister Theresa May's country retreat Chequers in Buckinghamshire.
The couple will attend a gala dinner at Blenheim Palace out in the countryside on Thursday evening. These will focus on relations with Russian Federation, trade, Brexit and the Middle East.More news: "US Not Treated Fairly But I believe In NATO", Says Trump
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