As he stood in a packed Trafalgar Square next to his 16ft robot of Donald Trump sitting on the loo, Don Lessem appeared momentarily worried by its popularity.

The 67-year-old American had shipped his newly-made $25,000 (£19,600) creation to the UK for the mass protests against the state visit of the US president.

But, as the talking model became a focal point for demonstrators in central London, Mr Lessem – a dinosaur expert whose company designs animatronic versions of the prehistoric animals – wondered what it might mean for his own legacy.

“I’ve written 50 books on dinosaurs and worked on Jurassic Park,” the Philadelphia-native told The Independent. “But I’m starting to think I might just end up being the guy who put Trump on a giant toilet.”

He looked round at the crowds. “Absolutely worth it,” he concluded with a wink.

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Such was the spirit of this carnival of resistance, which saw 75,000 people descend on the capital to denounce the three days of pomp and ceremony being granted to this most divisive of US presidents.

Mr Lessem flew his robot in because his mother, long ago, fled the holocaust in Europe. “She sees similar things in Trump that she saw in Hitler back then,” he said.

But people came from far and wide on a drizzly Tuesday to support a whole variety of causes which, they say, Mr Trump’s presidency endangers: climate change action, LGBT+ rights, Middle East peace, and freedom from ending up with a chlorinated chicken on one’s dinner plate, chief among them.

They came chanting, cheering, jeering and waving an admirable number of placards making reference to small hands and big wigs. “The toupee is fine,” read one. “But the asshole under it has to go”.

Here, in short, was British anger, British humour and not a small amount of British incredulity when news filtered through from a press conference – literally being held around the corner at the Foreign Office – that the man himself had denied such a large-scale protest was taking place.

“A very, very small group of people,” the US president said at about the exact time the massed throngs were marching through Whitehall. “Fake news.”

“If someone opens the window for him, he’ll be able to hear there is nothing fake about this,” said Yonni Wilson, 60, of Maidenhead, “The man is a born liar. There is nothing good to be said for him.”

It was a view, unsurprisingly enough, widely expressed through the day.

“Not even worth a milkshake,” is how Richard Winslade’s placard summed up his own views.

“It’s the first protest I’ve ever actually been on,” he said. “And I’m 50, so this is a turnaround. But I just feel people need to speak up, not just against the man himself, but against everything he stands for. He’s a danger to the world.”

The clerk, from Bedford, had come along with his 22-year-old daughter.

“We wanted to show the world that the £25m being spent on this visit is not projecting the image of the UK that most people here believe in,” she said.

Among the highlights of this carnival of resistance were – but of course – the now-famous Trump baby blimp, and a singer who noted, in the form of a cheerful little ditty, that if a kingdom is run by a king and a principality by a prince, then it is perhaps fitting Donald Trump runs a “big country” – “work it out, people”.

Pro and anti-Trump groups scuffle on Whitehall amid demonstrations

Speakers, taking to stages in Whitehall and Parliament Square meanwhile, included journalist Owen Jones, Green MP Caroline Lucas, and shadow home secretary Diane Abbott.

Generally, they ticked the crowd-pleasing boxes of calling Trump a racist and homophobe; praising immigration and the NHS; and then making way for the next person. Frances O’Grady, general secretary of the TUC, elicited an especially big cheer for labelling the president a “dirty old man”. Those who went off-piste from such a formula tended to lose the crowd’s attention. A bit like when a band plays the B-sides at a festival, noted one wag.

By the same analogy, Jeremy Corbyn was clearly the headline.

Nonetheless, his announcement at the very start of his speech that he was “absolutely not refusing to meet anybody” – not even Trump, presumably – seemed somewhat out of place. Hadn’t he literally just boycotted the royal banquet?

Either way, perhaps this was a pre-emptive announcement. Shortly after, it emerged that the Labour leader had actually requested a meeting with the US president (turned down) during his visit here.

No matter.

Out in the crowd, Tom Stewart was down from Reading on his birthday.

“It’s not exactly how I’d chose to spend it,” the 32-year-old archaeologist said while waving a placard declaring that Barack Obama was a better golfer than his White House successor. “But this felt like a chance to say that the whole way the world is going – this rise of populism, eating away at hard-won rights – is wrong.

“Trumpism is just one manifestation of that. It’s happening in so many places. But as the supposed leader of the free world, it feels dangerous that America is going down this road. We have to speak out against it.”

Harper Smith felt the same. And, as a nine-year-old – and probably one of the youngest people at the protest – she has a bigger stake in the future than many.

Mum Nadya had taken her out of home-schooling for the day to bring the youngster. “Coming to a protest is an education in itself,” she said. “She’s learning so much today.”

Key among that, the 43-year-old screen printer reckoned, was the fact that “just because the royal family and British politicians are pandering to this bully doesn’t mean that it’s the right thing to do. It’s not.”

Trump supporter is milkshaked by aggressive crowd during Parliament Square protest

As for Harper herself? Was she enjoying her first protest? “Loving it,” she said. “Although I wish I was taller so I could see the stage.”

Plenty of adults felt the same.

It wasn’t all love and peace, it should be said.

A crowd of Trump-supporting counter-protestors were barricaded in a Wetherspoons pub by police after becoming involved in a disturbance, while separately, one attendee – proving that demonstrators at Brexiteer rallies don’t have a monopoly on questionable placards – carried a sign saying: “They all work for Rothschild”.

Less controversial but nonetheless chilling was a group of friends dressed as the handmaids from Margaret Atwood’s dystopian fascist novel.

“We’re trying to show that from here to that sort of future, it’s only a few short steps,” said one Jessica Branch, of London. “If people don’t speak out, that is how we end up.”

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The paradox to all this, of course, may be that not a single protester The Independent spoke to had taken to the streets when the leaders of countries like China, Kuwait or the UAE had been granted state visits – despite those states presiding over horrific human rights violations and abuses of freedoms.

“That is a contradiction,” said Jacqui Day, a retired vet, when it was put to her. “But America is supposed to lead the free world. If the US president is a bigot, what hope the rest of us?”

Besides, she said, both those visits took place some years ago, before what seems to be, on the back of Brexit and Mr Trump’s presidency, a new age of protest.