Is Boris Johnson really deploying a ‘diversionary tactic’ in announcing vaccine passports on the day he has had to perform a volte-face over a Christmas party in Downing Street? After watching his press conference tonight, I’m not so sure, though not because of the explanation the Prime Minister himself offered. He was asked about this accusation, which was first levelled by one of his own MPs, William Wragg, at PMQs. Johnson’s response was to ask journalists to imagine what it would have been like if today’s political row had forced a delay of the ‘Plan B’ measures to contain the spread of Covid this winter.

But the press conference, and indeed the substance of the measures being announced, underlined the flaw in the alleged ‘diversion’. It not only draws attention to the charge that this government doesn’t even bother following its own rules, but also makes it harder for Johnson and his colleagues to set certain rules at all. Why, for instance, did he this evening ask people to work from home if they could, but also tell them that Christmas parties are fine to go ahead? Even the most informal workplace would struggle to compete with the personal contact that tends to take place at a boozy Christmas party. The only possible explanation is that Johnson accepts he does not have the authority to tell people to cancel parties when one of his senior aides, Allegra Stratton, has just had to resign over a video in which she and No. 10 colleagues joked about a Christmas party that took place when such gatherings were clearly against the rules.

Chief medical officer Professor Chris Whitty and chief scientific adviser Sir Patrick Vallance were alongside Johnson at tonight’s briefing and they were keen to stress not just that people should get their booster shots, but also that the public weren’t really likely to disregard the guidance because of alleged rule-breaking in Downing Street. This may well be true: voters continued to support lockdowns after the Barnard Castle incident involving Dominic Cummings after all. But you only needed to cross the road to the Commons to see the damage that this Christmas party has caused: a parth that apparently both didn’t take place and also magically conformed to all the rules.

Health Secretary Sajid Javid had to listen to calls of ‘resign!’ as he announced the new restrictions — and not from opposition MPs but from his own side. Covid Recovery Group chair Mark Harper asked why the public should ‘do things that people working in No. 10 Downing Street are not prepared to do’. It was tricky for Javid to answer that. It will be trickier still if allegations of other parties in Downing Street get the same treatment that has dragged out this one over a week. This row isn’t going away. And neither is Covid. But at least the Prime Minister and his colleagues have the ability to take control over the former — if they choose to.