Partygate: How much political danger is Boris Johnson in?

“My hunch is it’s in the high 40s.”

So says a Conservative MP to me, as we indulge in a spot of guesswork about how many Tory MPs might have formally requested a vote of confidence in the prime minister.

What we are witnessing right now are the aftershocks, the tremors provoked by the publication of the report into pandemic parties on Boris Johnson’s watch.

For months, many Conservative MPs – who collectively have the capacity to give their leader the boot – invoked the name of the senior civil servant tasked with the inquiry: let’s wait for Sue Gray, they would say.

Well, her words and pictures have sprung into the spring sunshine and provoked a dance. Some of those steps we are seeing in public, with a handful of MPs saying publicly for the first time Mr Johnson’s time is up.

Plenty more such steps are happening privately. So, here are the numbers that matter.

For Conservative MPs to try to topple a leader, 15% of them have to write to the chair of the party’s 1922 Committee, which represents backbench Tory MPs.

Fifteen percent of the current number is 54 MPs. And the chairman of the committee in question is Sir Graham Brady.

Sir Graham – depending on your point of view – is admirably or frustratingly discreet about how many bits of correspondence he has rattling around in his jacket pocket.

All we can say definitively is 54 hasn’t been reached yet, or we’d soon be hearing about it.

Nature abhors a vacuum. And Westminster’s solution is a vast quantity of speculation. Journalists, MPs, advisers – we all do it.

And so you get the political equivalent of that children’s party game Pin the Tail on The Donkey.

Remember it? You have a blindfold put on you, get spun round half a dozen times, and then try to stick the furry fly swatter somewhere close to where an anatomical diagram would suggest it should be.

But your very best effort has it protruding from the beast’s forehead.

Well, a little like the unfortunate creature sporting an appendage in an unlikely location, MPs’ best efforts at guessing the number of letters submitted are exactly that – guesses.

And the whole thing is complicated further because some people have put in letters and then taken them out again.

Others have put them in, but only just said so publicly. So the number appears to have gone up, but actually it hasn’t.

Others have talked about writing a letter, but not yet got round to it, or decided against it. And plenty have absolutely no intention of doing so.

And even if 54 letters are sent, and a vote of confidence happens – assuming Boris Johnson doesn’t resign at this point – another 126 MPs on top of those who sent letters would need to join those original grumblers in voting to get shut of him for him to be a goner.

54 + 126 = 180, which is half of all Conservative MPs plus one more – i.e. a majority.

That is a high bar: 126 MPs who didn’t feel sufficiently strongly to put in a letter who then decide they want him removed.