Thousands of protesters have taken to the streets to call on Theresa May to end her "collusion" with Donald Trump.
Demonstrators urged the prime minister to withdraw her controversial invitation of a state visit to Mr Trump and denounced his travel ban as "racist".
The march, organised by the Stop the War Coalition, Stand Up to Racism and the Muslim Association of Britain, amongst others, set off from the US embassy in central London towards Downing Street on Saturday afternoon.
Protesters brandished placards declaring "No to scapegoating Muslims" and "No to Trump, No to War", while they chanted "Theresa May shame on you".
The prime minister invited the American president to visit Britain later this year during a recent trip to the White House.
Hours later, Mr Trump introduced a 90-day travel ban on residents from seven predominantly Muslim countries - Iraq, Syria, Iran, Sudan, Libya, Somalia and Yemen - to stop "radical Islamic terrorists" from coming to America, sparking fury.
A petition calling on the government to prevent Mr Trump from making a state visit because it would cause "embarrassment" to the Queen has received more than 1.8 million signatures.
Downing Street rejected claims the Queen has been put in a difficult position due to the invitation and insisted the state visit would go ahead this year, but MPs will debate the matter later this month.
Since the ban was announced, there have been protests at several US airports where travellers were being held, including at least 2,000 protesters at New York's Kennedy International Airport, while thousands took to the streets of the UK amid anger over the ban.
Kevin Courtney, NUT general secretary, told the crowds that Mr Trump's policies were aimed at "stoking up fear".
He said that the "fear and division" was evident in schools and told the masses gathered: "I'm here to say that every teacher should be involved in the campaign against Trump."
"We can fight Trump's policies, we can fight that division," Mr Courtney added.
Dawn Butler, MP for Brent Central, told the crowds that Mrs May needed to "understand the responsibility" of the UK's relationship with the US.
She added: "The answer isn't walls and the answer isn't bans".
The crowds marched down Park Lane - filling the length of the famous London street - and along Piccadilly towards Downing Street.
They chanted "Donald Trump has got to go" and "No ban, no wall" as they went.