Tens of thousands of people from around the country are preparing for a mass rally, with coaches laid on to ferry people from at least 15 cities including Oxford, Belfast and Edinburgh on Tuesday morning.
Other rallies are also planned in cities around Britain on Monday when Mr Trump arrives, as well as the next day when he will have talks with Theresa May in Downing Street and hold a joint press conference.
On Wednesday protesters will converge on Portsmouth when Mr Trump attends D-Day commemorations.
Activists say his invitation is “an insult to those who died fighting fascism”.
Last year an estimated 250,000 people marched through London to object to Mr Trump’s working trip, but next week’s visit – during which the president will granted full pomp and ceremony – is even more controversial.
Security will be extremely tight for the three-day event, but more than 150 people have pledged to attend a “Milkshakes Against Trump” gathering in Trafalgar Square, organised by a group called Milkshakes Against Racism.
However, they are unlikely to get close enough to the president to throw one, since they will be held behind a barrier about 100 metres from the gates of Downing Street.
According to a survey two weeks ago, more than a million Londoners said they were ready to protest against Mr Trump’s visit, while Commons speaker John Bercow and Jeremy Corbyn said they would boycott the banquet at Buckingham Palace.
Coaches on Tuesday will also take people to London from Swansea, Manchester, Newcastle, York, Leeds, Derbyshire and Sheffield, among others.
Demonstrators with placards from a coalition of groups called Together Against Trump will assemble in Trafalgar Square before marching to Whitehall.
Antiracism protesters will build a wall of cardboard to symbolically knock down, which they say represents the president’s Mexico wall and other policies.
After negotiations with police, the crowd is being allowed to march partway down Whitehall as the president has talks and lunch with Mrs May. Initially police had said they would allow only 700 protesters there.
The demonstration will then move to Parliament Square via Embankment.
Denis Fernando, of Stand Up to Trump, said they were not concerned that their actions might be rude to Mr Trump because the president had offended swathes of people.
“What he’s said and done is beyond rude, beyond pleasantries, he’s posing a threat to people. If you put together all the people Trump has in some way expressed bigotry towards, you have the majority of the population.
“Thousands of protesters will be marching to surround Trump as he joins Theresa May on a visit most believe should never have happened.
“We will be bringing central London to a standstill.
“By the time he leaves he will know - and the world will know – that people here reject him and his toxic politics.”
The cost of policing the trip will be high. “It is too early to speculate about the cost of the policing and security operation at this stage, but it will be significant,” a Met Police statement said.
“A very experienced command team is preparing the multi-faceted policing and security operation for the president’s visit, and whilst the Met has a responsibility to ensure the right to lawful protest, this needs to be balanced with the complex requirements of this policing plan,” it added.
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