How easily will Rebecca Long-Bailey win the nominations of the two affiliates she needs to qualify for the final round of the Labour leadership election? One endorsement the shadow business secretary will be banking on is Aslef, the train drivers’ union. It twice nominated Corbyn and endorsed a Leave vote in 2016 to boot, which suggests its nomination has only one destination.

The New Statesman understands, however, that opinion within Aslef is not quite unanimous this time. Mick Whelan, its general secretary, told Sky News last week that he was not sure who the union would back. He was not playing for time but attesting to genuine uncertainty. He is drawn to Keir Starmer on the grounds that he is likeliest to win a general election. His eight-strong executive, meanwhile, is likelier to plump for Long-Bailey.

Unlike Whelan, who can only make recommendations to his ruling body, executive members have a vote. As was the case in 2016 - when it voted by a margin of five to three to endorse Brexit - he will have to wear his union’s decision if it does choose differently. As such, the odds are stacked against Starmer denying Long-Bailey Aslef’s nomination, which is widely considered to be hers already. But the fact that a debate exists, even in a devoutly Corbynite union, is a mark of the race’s unpredictability.