If Donald Trump had been inclined to wind down a bullet-proof window in The Beast as he passed through central London, he may well have wound it straight back up.
The public were kept a long way from his motorcade but the boos were loud, the placards stark and the general message expletive-laden.
And beyond that, in Parliament Square, under the gaze of a statue of a hunched Winston Churchill, British satire was on display.
A Donald Trump baby blimp rocked back and forth in a light wind.
A man was dressed as a caged gorilla with a Donald Trump face mask while his companion pulled off an impression of Boris Johnson - the MP who wants to be the next UK prime minister - dressed in a striped prison uniform.
There were toilet rolls for sale bearing the president's face, sold for two for £5 from a couple of supermarket trolleys.
A police officer went above and beyond to hand out Haribo sweets to his colleagues standing in a neat line along Whitehall.
Above them, builders in hard hats watched events unfold from the scaffolding encasing Big Ben.
It was all very British.
But it wasn't just the British who were there to protest.
US holidaymakers gave up a day's sightseeing in the capital to let their president know what they thought of him.
Nineteen-year-old student Jess Renner, who was too young to vote in the last US presidential election, headed down to the protest from her nearby hotel with her mum.
"It was fun to come and flip him off," she said. "He's a bully and he's trying to bully you guys into buying all our stuff."
Fellow American Robert Kihm, from Denver, Colorado, said having Mr Trump for a president was no longer funny.
"It's embarrassing and ultimately frightening."
What's your message to him? "Where do I start," he replied, in exasperation.
"Stop being authoritarian, respect the rule of law and stick to the norms for a US president," he urged.
A group from Belgium on a three-day trip to London also couldn't resist having their say.
"He said Brussels was a hell-hole so we are also very against him," said Annelie Comeyne, from Ghent.
Not everyone felt the same.
A minority, including Lorraine Chapel, from Chiswick, in west London, was there to welcome the president.
"Love him or hate him, Mr Trump runs America and he is here by invite from the Queen," she said, waving her handmade sign.
The blimp of a baby Donald was offensive, she said. "Suppose they did that for the Queen in America".
In a flash, things turned rather ugly when a woman appeared next to Ms Chapel, accusing her in strongly-worded terms of supporting misogyny.
Meanwhile, a heated exchange played out in the background as Trump supporters took on anti-Trump protesters before the debate veered back to domestic arguments around Brexit.
A little later, the atmosphere lifted as speakers took to a temporary stage outside Downing Street where Mr Trump was holding talks with the outgoing Prime Minister Theresa May.
"Say it loud, say it clear," the speaker shouted over the microphone, as the rain kept falling.
"Donald Trump's not welcome here," the crowd hollered back, from under hoods and umbrellas.
Some had their faces covered with #trumpstinks masks, others wore badges saying "another nasty woman against Trump".
There was whooping and whistling as police officers cautiously managed the growing numbers, opening and closing routes.
Mothers with small children in buggies rubbed shoulders with seasoned protesters and American ex-pats.
Melissa Branzburg, originally from Miami but now living in Greenwich, said President Trump has been talked about in her house for a long time.
Her children - Isaac, five, and Ruth, three - would usually be doing crafts or playing in the park but today they were getting a lesson in political activism.
They were keen to let Mr Trump know they didn't want him here in London, said Ms Branzburg.
They asked a lot about children behind bars in the US, something she tried to explain in age-appropriate language.
"I want them to know they can make their voices heard and can see that other people agree with them," she added.
Florence Iwegbue, a dual US-British citizen, wore bright pink feathers in her hair and red, white and blue glitter on her cheek.
She said she feared Britain might be following too closely in US footsteps.
"The message is not getting through that the way of life in America does not work," she said.
"In the US, you can't afford to be poor, sick, black or brown. This is becoming an issue in Britain - and it needs to be dialled back."