Three resignations were expected - one was not.
That was the departure of Boris Johnson's long-standing Policy Advisor, Munira Mirza, who walked over his refusal to apologise for the smear against opposition leader Kier Starmer, that he had refused to prosecute serial sex offender and television presenter Jimmy Saville whilst serving as the Director of Public Prosecutions.
Friends and allies of the Prime Minster have been asking him for days - often in public - to take back the remarks and apologise to Mr Starmer, but to no avail.
In her resignation letter, Ms Mirza wrote: "You are a better man than your detractors will ever understand, which is why it is desperately sad that you let yourself down by making a scurrilous accusation against the leader of the opposition".
Calling for Mr Johnson to apologise, even now she wrote: "It's not too late for you but, I'm sorry to say, it is too late for me."
Coming from a loyal lieutenant - with him since his time as Mayor of London - this will have stung.
However, it didn't sting him into an apology.
Instead, it appears to have triggered a wave of "resignations" by the top management tier in Downing Street. All three had been expected to be shown the door over the 'Partygate' affair and other causes of disquiet in Downing Street.
Jack Doyle, the Director of Communications was the first to go. He had already offered his resignation, for handing out prizes at one of the Christmas parties investigated in the "Partygate" affair, but the Prime Minister had refused to accept it. Until tonight.
Then, in a move that surprised absolutely nobody in Westminster, his Principal Private Secretary - the top civil servant in Number 10 - quit.
Martin Reynolds - nicknamed 'Party Marty' - was the one who circulated the notorious "Bring your own Booze" invitation to almost 100 Downing Street staffers in June 2020.
He had been heavily briefed against since December, and was always likely to take the fall for 'Partygate'.
Dominic Cummings claims he had been urging Mr Johnson to get rid of him since early 2020, and claims to have cited the BYOB e-mail as proof that Downing Street was not being run properly on the very day it was sent.
Dan Rosenfield, the Prime Minister's Chief of Staff, was also heavily briefed against, particularly by Special Advisers (SPADs in Westminster-speak) who didn't like his style.
Tonight, allies of the Prime Minster are praising him for "taking action", in what looks like a co-ordinated campaign on Twitter.
They say that he promised a clear-out of top advisers in Number 10, and a re-set of the entire operation.
On Monday, there was a promise in the House of Commons to establish a Department of the Prime Minister - similar to the Department of An Taoiseach.
But enemies of Boris Johnson see the same events and draw radically different conclusions.
Dominic Cummings tweeted: "The bunker is collapsing."
Meanwhile, more MPs are coming out and saying they have sent a letter to the 1922 Committee of backbenchers calling for a no-confidence vote in the party leader.
