When David Davis and Boris Johnson met on Thursday at a summer party thrown by The Spectator, they confronted each other not as colleagues but like the US and Russian armies coming together on the Elbe in 1945 — erstwhile allies who knew they were now political rivals.

There was bonhomie, much of it forced, as the Brexit secretary joked that the foreign secretary was “a failure”. Johnson was visibly irritated as Davis flirted with and then embraced his sister, Rachel Johnson, a journalist who made waves last year by opposing her brother on Brexit and then joining the Lib Dems.

Davis told Johnson, “You’re too toxic for your own sister,” and boasted that he had persuaded Rachel to defect back to the Conservatives. “Boris