Even before Boris Johnson learnt, at around midnight on Thursday, that he had tested positive for the coronavirus, it had already infected the government at its highest levels, changing the way people work and contributing to a feeling of embattlement. “It has made real for everyone out there what was already happening inside,” said a government aide. “Huge numbers of people are working from home or wondering when they are going to get it.” It was hard for many not to feel their spirits sink as their leader fell ill during the battle with an unseen enemy.

Johnson chaired Friday’s 9.15am meeting of his Covid-19 “war cabinet” by video link from his flat above No 11, where he is now self-isolating, plates of food being