On Friday, demonstrators are expected to gather near Chequers, the Prime Minister's country residence, where May and Trump will hold a working lunch.
Trump and his wife, First Lady Melania, will land at London's Stanstead airport after attending a North Atlantic Treaty Organisation summit in Brussels.
Some cited "job restrictions" while another said he was wary of the press. The 47-year-old disembarked from her plane in a trench coat - a classic item which retails at £1450 from Burberry - one the UK's most recognisable designers.
The president will be accompanied by up to 1000 staff, a motorcade and multiple helicopters during his trip. The U.S. president is expected to attend a formal dinner at Blenheim Palace in Oxfordshire with the business leaders, along with the senior members of the cabinet.
Asked about Trump's comments at a hastily-arranged meeting with journalists, May said she was delivering wishes of the British people.
"I think it's fine", Trump said. A lot of people like me there.
"He's been very, very nice to me, very supportive". While saying that he didn't have any message or advice, he added: "I would say Brexit is Brexit..."
The shadow policing minister, Labour MP Louise Haigh, said, "It has emerged that officers being accommodated in Essex are sleeping on cots in squash courts, 100 female officers with four toilets between them, likely to be sleeping on mats tonight, 300 male officers with five toilets between them".
They will then meet the Queen for the first time, at Windsor Castle, before heading to Scotland where the USA president will spend the weekend at his Turnberry golf course in Ayrshire. Their first stop was to the ambassador's official residence at Winfield House in London, while being carefully protected from protesters.
Trump will then spend a private weekend in Scotland with his wife, where he owns two golf resorts.
US President Donald Trump arrived in "hot spot" Britain on Thursday after casting doubt on Prime Minister Theresa May's plans for leaving the European Union and with protests planned across the country where he says the people like him a lot.
And he made clear that he did not approve of the softer stance the PM has been advocating despite fury from many Tory MPs. The EU better be careful. "But maybe they're taking a little bit of a different route, so I don't know if that's what they voted for". Picture: GettyAmnesty International unveil a banner on the Vauxhall Bridge.
Protests will culminate in a 70,000-strong march through London from Portland Place to Trafalgar Square.
Dick said: "We will keep him safe".
Dick said: "Later today we have a visiting head of state from across the pond".
"On Saturday there will be sort-of related protests (from the) far-right and far-left and probably the most hard".
The plans laid out Thursday in a 98-page government paper gave Britain's most detailed answer yet to the question of what will replace them.
A giant six-metre-high blimp of Trump depicted as an orange baby in nappies is also expected to fly over the capital.
Almost every force in England and Wales has contributed officers to help with the massive mobilisation, the biggest since the 2011 riots.
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.
A leaflet for a protest against Donald Trump is seen amongst Labour party flags at the Solidarity Tent at Labour Live, White Hart Lane, Tottenham on June 16, 2018 in London, England.
Before the Sun interview was published, May invoked Winston Churchill as she addressed Trump and business leaders at a black-tie dinner at Blenheim Palace, the grand 18th-century country house which was the British World War Two leader's birthplace.
"This week we have an opportunity to deepen this unique trading relationship and begin discussions about how we will forge a strengthened, ambitious and future-proof trade partnership".