“Was a Christmas party thrown in Downing Street for dozens of people on December the 18th?” Only a Puritan Leader of the Opposition could begin PMQs with such a question.

Sir Keir Starmer attempted to sound as unpuritannical as he could, but his principles were clear. Pleasure must invariably yield to duty, Christmas parties must be sacrificed so the letter of the law can be upheld, rules are not made to be broken.

Boris Johnson replied that “all guidance” – a more flexible concept than rules – “was followed completely”, and urged Sir Keir to do the same with “his own Christmas party which he’s advertised for December the 15th, but to which, unaccountably, he’s failed to invite the Deputy Leader.”

As the Prime Minister said this, he jabbed his finger at Angela Rayner, sitting on the Opposition front bench, and could not avoid laughing at his own joke.

“Nice try but that won’t work,” Sir Keir replied, attempting once more to sound like a relaxed Puritan. He has become rather good at doing so: as his allies observe with pride, he is “demonstrating increased spontaneity”.

But soon he was in earnest again, accusing Johnson of having “one rule for them, another for everyone else”.

What the Puritan never understands is that “everyone else” might enjoy going to Christmas parties – a form of festivity which is usually more enjoyable for junior staff than for those at the top of the hierarchy.

Lord Macaulay said in his History of England, “The Puritan hated bearbaiting, not because it gave pain to the bear, but because it gave pleasure to the spectators.”

The Leader of the Opposition is in danger of seeming to oppose Christmas parties not just because they might be against the rules, but because they might give pleasure to people.

Johnson accused Sir Keir of drivelling on irrelevantly and wanting to take the country back into lockdown.

Ian Blackford, for the SNP, declared in his most sententious manner that it was “deeply regrettable” to have “to spend so much time discussing the Prime Minister’s misconduct”, and accused him of hosting “a packed party in Downing Street”.

So we saw two Puritans coming out against Christmas parties. Outside Westminster Hall, a baffled party of Chinese tourists noticed Oliver Cromwell giving a nod of approval.

Sir Ed Davey, for the Liberal Democrats, advocated paying more money to farmers, a cause connected to the Lib Dems’ hopes of victory in the forthcoming North Shropshire by-election.