Jeremy Corbyn will soon be prime minister. Or so, at any rate, says Jeremy Corbyn. He’s absolutely convinced of it. The next election, the Labour leader keeps boasting to his supporters, is in the bag. “This is a movement,” he proclaimed at a rally in Hastings on Saturday, “that will win the next general election.” Not “can” win. “Will” win.

In private, apparently, he’s even more sure of himself. “I said to him, ‘When are you going to be prime minister?’” revealed Michael Eavis, the organiser of the Glastonbury Festival, a week ago. “He said, ‘In six months.’”

This afternoon in the Commons, Mr Corbyn continued to bask in the inevitability of his triumph. He’d come to watch Home Office Questions, where Amber Rudd, the Home Secretary, began by congratulating the Labour MPs Mr Corbyn had just appointed as shadow ministers.

“Could I take the opportunity of welcoming the shadow front bench’s new team – the members for Torfaen, Derby North, Sheffield Heeley and Manchester Gorton?” said Mrs Rudd pleasantly.

Mr Corbyn curled his lip. “They’ll be ministers soon!” he crowed.

A minor moment, but telling. It seems that the Labour leader is now so confident of electoral victory that even when a Government minister is being polite and friendly, he heckles to inform her that she’ll soon be out of a job.