Another day, another reminder that Donald Trump is a menace to the American constitutional order. His sacking of the acting attorney general, Sally Yates, has overtones of Richard Nixon: except, of course, that Trump’s presidency will make Nixon look like a paragon of integrity by the time it is finally over. Trump’s already infamous executive order – the beginning of the implementation of his explicit pledge to ban Muslims from entering the United States – has been widely condemned on constitutional and legal grounds. Yates instructed her department not to enforce the order because she was not “convinced that the executive order is lawful”: and so she was purged.

Many US presidents have been responsible for injustices at home, and even graver injustices abroad. It nonetheless needs repeating – until we are blue in the face – that this is not a normal president. The usual playbook of opposition does not apply to an authoritarian, bigoted demagogue who does not conform to democratic norms. A proto-fascist will not be defeated by a few rousing renditions of Kumbaya.

There will be those in Britain who say: this is none of our business – Trump is for Americans to deal with. His whopping loss in the popular vote aside, he triumphed in the US election. Americans are not exactly known for appreciating foreigners sticking their noses into their internal affairs, least of all Brits, given the small matter of the war of independence, and the fact that British troops burned down the White House in 1814.

Of course Americans must lead the movement against their president. We’ve already seen an unprecedented number of Americans protesting: in the Women’s March and in spontaneous demonstrations against the executive order. This is heartening, and the very least we can do is express our solidarity.

But we must mobilise, too. Because of Theresa May’s determination to exit the single market, our prime minister is making a strategic decision to ally with Trump’s administration. She waltzed off to the White House almost as soon as he’d moved in, played a sycophant, held hands with him, praised him for offering his country renewal, then refused to promptly speak out against his executive order, even when her own citizens had been targeted.

“We will be offered a favourable trade deal!” the government says about a US president whose new defining slogan is “America first”. “We will restrain him!” they say, just as was naively said about Tony Blair and George W Bush. The fact is, Britain is being used to legitimise and normalise the president. Our weak, cowardly government is turning our country into a useful prop for Trump.

How demeaning of our country, to be reduced to a patsy for a racist demagogue. That is why we have a responsibility to challenge our government’s attempt to turn Britain into Trump’s stooge. Last night’s astonishingly attended impromptu protests in dozens of towns and cities around the UK was just the beginning. A Stand Up To Trump coalition is now being formed: watch this space. Thousands turned out to protest with barely 36 hours’ notice. When Trump arrives on his state visit, we can expect one of the biggest demonstrations in British history.

May, bizarrely failing to remember how Blair’s alliance with Bush sank his premiership, believed she pulled off a grand coup last week at the White House. It’s up to us to ensure history judges it to be a fatal mistake.