Worrying news from Westminster, where it seems the Omicron variant of Covid-19 is able to escape not just vaccines, but also the far more powerful shield offered by the convivial and fraternal spirit of the Conservative Party. We knew this because Jacob Rees-Mogg had finally given in and put on a facemask for Prime Minister’s Questions. Indeed, the vast majority of Conservative MPs were, finally, following the guidance put in place by the (lest we forget) Conservative government.

They put on a decent show of initial unity, groaning theatrically when Keir Starmer opened by asking about the Mirror’s report that Number 10 had their own lockdown-busting party last Christmas. On the far back bench behind Boris Johnson, Alec Shelbrooke was almost horizontal with contempt at the Labour leader, hoisting himself upright only as the prime minister began to reply.

The benches behind him roared with delight at this debating point worthy of Cicero

“What I can tell the right honourable gentleman,” Johnson began, as though the details of his office Christmas quiz were so sensitive that his comments had to be censored in case the Chinese were listening in, “is that all guidance was followed completely.”

Connoisseurs of Johnson’s ongoing struggle with his own rules will recognise that this is what he usually says for about a week before he admits the guidance was largely ignored.

Anyway, the prime minister asked, why hadn’t Starmer invited his estranged deputy, Angela Rayner, to his own party this Christmas? The benches behind him roared with delight at this debating point worthy of Cicero.

Starmer tried again. “Does the prime minister really expect the country to believe that while people were banned from seeing their loved ones at Christmas last year, it was fine for him and his friends to throw a boozy party in Downing Street?”

Johnson went for bluster. “I’ve said what I’ve said about Number 10,” he said, in what was pretty much a confirmation of the Mirror’s story. Anyway, it was all a long time ago.

“One rule for them, another rule for everybody else,” observed Starmer. It’s a critique he’s been using a lot lately. He switched to another line of attack. He wanted to know whether an internal report had indeed concluded that the Johnson target of 40 new hospitals was likely to be missed.

“No!” cried the prime minister, to Tory cheers, before accusing Starmer of asking “frivolous questions,” which was a bit much from someone who’d just been trying to score debating points about party invites. Next to him Sunak looked a little cautious.

Starmer had an ace up his sleeve, a leaked document from the Department of Health explaining how, in essence, refurbishing a hospital could be described as delivering a new one. Johnson replied that everyone had always known that the new hospitals weren’t actually new.

Had they, though? The Tory backbenches had gone quiet. Hospitals are a live wire in politics: no one wants their local one closed, and it’s quite tricky to persuade voters that you’ve built one when you haven’t. They tend to notice.

When Johnson gave his final reply to Starmer, Tory MPs naturally called for more. The noise in the chamber is with the prime minister. But the Labour front bench, newly reorganised, looked ready for a fight too. Starmer has his attack lines on Johnson: one rule for him, and he doesn’t keep his promises. They have the virtue of both feeling and being true. Meanwhile Tory whips are struggling to get supportive questions asked. Instead there were two from Conservatives about why their local councils hadn’t got levelling-up money. Andrew Rosindell asked about migrants in the Channel. Real problems that can’t be blustered away.

Perhaps Rees-Mogg was right all along, and the reason Conservative MPs have to wear facemasks these days is that they’re simply feeling rather less convivial and fraternal.