When Boris Johnson chants his mantra of delivering Brexit, uniting the country and beating Jeremy Corbyn, it is very much a personal imperative. For the simple reason that if he fails, as many of his colleagues anticipate, he will look like a blithering idiot.

The point is that back in the spring of 2016, he faced a nation-defining fork in the road, when he was dithering about whether to stick with the then PM David Cameron and fight to stay in the EU or lead the leave campaign.