London has long been seen as the canary in the Conservatives’ electoral coalmine, and the party is becoming increasingly panicked about the prospect, on 3 May, of said canary revealing itself to have been dead for ages.

In a few weeks, London will go to the polls in local elections, at which turnout is not expected to be higher than 30 per cent, and which are expected to end with the Labour Party taking control of local councils such as Westminster, Wandsworth and Kensington & Chelsea. These are the wealthiest enclaves of already wealthy London, where until recently Conservative candidates did not even have to bother troubling the portico’d doorsteps to be assured of victory.

Whatever happens a few weeks from now, those days are long gone, and its implications for Conservatives and Conservatism are bleak indeed.

Why Labour is expected to make these dramatic gains is complex to the point of being almost unanalysable. And because virtually all the political media live in it, degrees of nuance and complexity are extended to it which are never available to anywhere else. The politics of Scotland and Catalonia can be understood easily enough in an afternoon or 700 words, whichever is shorter. Not so London.

At the launch of Labour’s local election campaign on Monday morning, Sadiq Khan introduced Jeremy Corbyn as “the country’s next prime minister”. Eighteen months ago he was telling party members: “We cannot win with Corbyn, so I will be voting for Owen Smith.”

When Corbyn appeared, he spoke for 20 minutes and served yet again as the lightning rod for all of the world’s ills.

We live in times that feel increasingly like the late 1930s, and yet there is no international outrage severe enough that all the UK wants to talk about is Jeremy Corbyn’s role in it. Two weeks ago, the most pressing question over the chemical poisoning of a Russian double agent on British soil was Jeremy Corbyn’s weak response to it. Now the same questions are asked about the chemical attack on Syrian children and Eastern Ghouta. That Corbyn and the Labour Party will not come out and blame Assad or Putin for the attack appears now to be the most fundamentally important aspect of this dreadful incident.

Those who would prefer not to give Jeremy Corbyn the benefit of the doubt say he is naturally inclined to take the side of Assad or Putin, because they, like he, are opponents of America and the West.

Those inclined to see Corbyn’s worldview in a more positive light say he is simply a pacifist. That military intervention always makes things worse. No matter the events, however horrific, he will not take even the tiniest tiptoe down any road that leads towards British military involvement. It is for this reason, for example, that Hilary Benn came perilously close to being sacked from the shadow cabinet in 2015, for arguing in favour of British air strikes on Syria, which have now been shown to have been instrumental in diminishing Isis.

But London doesn’t greatly seem to care about any of this. Labour has been gaining MPs in London from 2005 onwards, even while losing elections overall. Two-thirds of its 72 MPs are Labour. Momentum activists are wildly overrepresented in London when compared with the rest of the country. London is young and ethnically diverse. It is either poor or prosperous but with a social conscience. It also, broadly speaking, hates Brexit.

On Monday morning, Corbyn made an impassioned plea to Britain’s “EU nationals”, whose rights “only Labour will guarantee” and the “disgrace that they have been used as a bargaining chip.”

That Jeremy Corbyn has been a hard Brexiteer for 30 years and would have triggered Article 50 on 24 June 2016, given the chance, a decision that would have had catastrophic implications for European nationals in Britain, is a subtlety too far for your average ballot box.

Demographic trends imply that politically, where London is will be where the country as a whole arrives in 20 or 30 years’ time.