It was the moment that Downing Street staff knew the Brexit talks were back on with a vengeance. The No 10 staff WhatsApp group was abuzz with comments reflecting incredulity at the rapid transformation. What prompted this outbreak of optimism was not the sight of Boris Johnson and the Irish premier Leo Varadkar deep in friendly conversation two days after the deal was declared dead, but the sight of Dominic Cummings in a suit. “We knew then that it was time for serious negotiations,” said a No 10 aide.

For a man who usually dresses more like the Extinction Rebellion protesters outside No 10 than the civil servants inside, it was a radical shift. “He looked like someone on a stag do who has to