If a bat’s squeak of self-pity can be detected in some of the prime minister’s tetchy responses to the leader of the opposition, that is understandable. Nothing is going according to plan: the triumphant post-Brexit birth of “Global Britain”, rumbustious crusader for free trade, has had to be postponed indefinitely. Boris Johnson finds himself presiding over a crisis where all the choices available are bad ones.

Thus the government has been forced to concede that the planned opening of all primary schools this month is not viable, as teachers’ representatives have been saying all along. At most, schools seem to be able to cope only with their first-year and final-year pupil intakes. More than that, and maintaining the necessary distance between pupils becomes impossible. This means that many parents will still be unable to return to their previous workplaces but must continue somehow to educate their children at home. That has consequences for the economy. But it is also damaging to the children themselves. Those already disadvantaged by poverty are bound to come off worst.