Thousands crammed the streets of central London on Friday to vent their anger over Donald Trump's first official visit to Britain, blowing horns, waving banners and hoisting a bright orange effigy of the US president on their shoulders.

Filing past palaces of high-end commerce - Apple, Burberry, Brooks Brothers - marchers criticised Trump's policies on immigration, climate change and torture, as well as his treatment of women. Some carried more than one sign, unable to choose which policy they hated the most.

The Reverend Nigel Sinclair, a 53-year-old Church of England preacher, came in what he called his Sunday vicar's outfit, carrying a sign that showed how Trump's ideas differ from those of Jesus Christ. Susie Mazur, 29, from Salisbury in southwestern England, crocheted a Donald Trump pin-cushion and wore it on her head, winning praise from fellow protesters.

"People coming here nowadays feel very hopeless about what is happening. They don't like what is happening in the UK, in America, across the world - there are so many problems," Mazur said. "Everyone has the same goal. What they want is to stop hate, basically."

As Trump met with Prime Minister Theresa May at her country retreat outside the city, the protesters gathered outside embassies, offices and homes carrying signs that read, "Human rights have no border," and "Mother Earth unites us," before marching past the shops of Regent's Street on their way to Piccadilly Circus and finally Trafalgar Square, which the city calls a "centre of national democracy and protest."

Not everyone was protesting against Trump, however.

Augustine Chukwuma Obodo, who wore a "Make America Great Again!" hat and a "Trump for President in 2020" shirt, said he wanted to make clear that not everyone found the protests amusing. Obodo, a Nigerian living in London, said he wanted to add his voice to those who are quieter, but believe Trump is doing a good job on issues such as pushing NATO members to increase their defence spending.

"America is not a cash point," he said.

The day began with a giant balloon that caricatured Trump as a screaming orange baby flying outside the Houses of Parliament. The nappy-clad infant, with a quiff of hair and a mobile phone for tweeting, was the centrepiece of demonstrations.

"Depicting Trump as a baby is a great way of targeting his fragile ego, and mocking him is our main motivation," said Matthew Bonner, one of the organisers of the balloon flight. "He doesn't seem to be affected by the moral outrage that comes from his behaviour and his policies. You can't reason with him, but you can ridicule him."

Hundreds crammed Parliament Square to take in the spectacle. Deborah Burns, 43, of Newcastle in northern England, brought along her 10-year old daughter, Monica Siddique.

"I think it's a good way to stop Trump from being mean to the rest of the world," Monica said of the balloon. "He says, 'Oh, this is a free world.' But then he goes and builds walls. ... He acts like a baby."