You might think a byelection showdown between two progressive parties is unimportant when the deep struggle for the national heart is between the right bloc and the left – but the result in Holborn and St Pancras matters. It matters for Andy Burnham and Labour because this is a test of the Burnham bounce: he saw off the right in Makerfield – can he win over the left too? Can he show he has enthusiastic approval from voters in southern constituencies as well as those in the north?

For the Greens it matters almost existentially because failing here could send them and their leader, Zack Polanski, back to the political fringes. Holborn and St Pancras, neighbouring Westminster, was vacated (vengefully) by Keir Starmer last week. This plum forever-Labour constituency has attracted 96 Labour applications for selection day on Wednesday, though not, it seems, nationally recognised names.

This is Labour’s to lose. And it might. The constituency was comfortably won in 2024 by Starmer; in May’s local elections the Greens took extra council seats, though Labour kept control and remained ahead by 10 percentage points. But byelections are idiosyncratic beasts in which voters risk nothing, electing neither council nor government. Few bother to turn out. For those who do, a byelection offers a free hit for whimsical preferences, “sending messages” on maverick issues or an urge to biff the government of the day.

A Labour loss would dent Burnham’s bounce, letting air out of his optimistic bubble. But frankly, losing here would be no........

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