“I welcome the Met’s decision to conduct its own investigation,” Boris Johnson told MPs at the start of his statement on Ukraine, completely plausibly. Which of us doesn’t welcome the news that we could be facing one or more £10,000 fines? Possibly the prime minister has already sent a discreet WhatsApp to Lord Brownlow asking how he’s fixed to help out with such matters, just until the money from the Shakespeare book comes through. Providing no one wants to buy any more cushions.

Why did Johnson welcome the attentions of the plod? “Because I believe this will help to give the public the clarity it needs and help to draw a line under matters.” Well, perhaps.

The problem is that the public already has the clarity it needs on the question of Club 10 Downing Street. This is why there are two groups of politicians desperate to keep Johnson in place. The first comprises those members of the Cabinet who know they’ll be following him out of the door. For instance the Chief Whip, Mark Spencer, should probably start taking his personal stuff home from the office now, to save having to carry it all out at once in a big box.

Imagine a TV producer trying to cast the minor role of “Tory MP” in a children’s drama

The second is Labour MPs, who can see the damage that Johnson is doing to his own party. From the point of view of Labour strategists, what could be better than Johnson staying at his desk for months, wearily explaining that he won’t know what he got up to until the police tell him what the charges are?

They can’t say that, obviously, so while the Tory end of “Operation Save Big Dog” involves Grant Shapps dazzling political journalists with his descriptions of how he has a spreadsheet containing the name of every Tory MP – every single one of them! – the Labour end is a touch more subtle. It involves Angela Rayner calling for Johnson to resign, thus forcing Conservatives to defend him.

So before the prime minister’s statement, parliament was treated, once again, to the sight of Paymaster General Michael Ellis explaining that his client was exercising his right to silence.

How to describe Ellis? Imagine a TV producer trying to cast the minor role of “Tory MP” in a children’s drama. The character in question has two lines and is barely on screen, but they need to radiate self-satisfaction as they explain to the kid heroes that the villain’s plan to pollute a city’s water supply simply isn’t any of their business. When Michael Ellis arrives for the audition, everyone else is sent home.

“I’m not in a position to comment on the nature or content of the police investigation,” Ellis began. He was keen to explain that he was a reasonable man. “I recognise the public anxiety and indignation that it appears as though the people who have been setting the rules may not have been following the rules,” he said, to loud laughter from the Labour benches. However, he explained, we would have to wait, not just for Sue Gray, but now for the police to finish their work.

Rayner’s job, replying to him, was to make sure that the muck was spread as wide as possible. “They are allowing this to happen,” she said, gesturing at the Tory benches. In an interesting twist on social distancing, Conservative MPs seemed to have clustered at the end of the chamber, as far from Ellis as they could get. They might be present, but a lot of them weren’t sure if they wanted to be involved.

Some, of course, were desperate to wade in. Perhaps there’s a sort of camaraderie in defending a hopeless cause. The line, broadly, was “How dare people ask questions about birthday cake as Europe stands on the brink of war?” Sir Edward Leigh had quite a good go at it, although in other circumstances, he’s the kind of fellow who might take a minister misleading parliament quite seriously.

Others got a bit confused. Richard Bacon said Johnson had committed “a relatively minor offence”, which is not quite the right line. Graham Stuart said Labour was only asking about parties because of their “absolute terror” at facing Johnson. Opposition MPs managed to stop quaking long enough to cheer at that one. Mark Jenkinson suggested that Johnson was the target of a plot by Labour and journalists, although even those of us with the most generous employers would have struggled to get that wine fridge through on expenses.

“Ten minutes of eating cake and wishing someone a happy birthday would not a party make”

Jacob Young said parliament ought to be talking about the horrific way energy bills were going up. It will be interesting to see how that one goes down on the doorstep: “I hear your complaint that our leader’s a hypocrite and a crook, but have you considered how much poorer you are this year?”

Lia Nici said voters in Great Grimsby were “happy, very happy, that essential workers have gathered together”. Perhaps they’re fundraising even now to buy Johnson another cake.

Ellis, meanwhile, was fending off Labour attacks. The birthday party might have been a “ten-minute coffee break,” he said. That was “one possible interpretation”. He expanded: “Ten minutes of eating cake and wishing someone a happy birthday would not a party make.” It’s weird that none of this came out in the lockdown guidance at the time. Presumably Johnson’s defence centres around the idea that a party doesn’t count unless you enjoyed it.

“A person in this country is innocent unless or until they are proven guilty!” Ellis proclaimed. This is true, but it’s not the only bar a prime minister has to jump. Still, maybe we can look forward to the Tories fighting the next election on that slogan. “The Conservatives: Nothing Was Ever Proved.” Labour would be very happy with that.