ANALYSIS: David Davis's resignation could be the beginning of the end for Theresa May
For Smart Alec's like me, David Davis's decision to finally leave the Government is something of a disappointment.
Never again will we be able to do those oh-so-clever tweets about the latest Brexit crisis being a "threatening to resign matter" for the Brexit Secretary.
How we laughed at the numerous occasions when "friends of DD" briefed he was on the verge of quitting. He quickly became the boy who cried wolf of British politics, making lots of noise about how he was on the verge of walking, but never actually doing it. Not any more.
His resignation, just 48 hours after Theresa May had appeared to finally win Cabinet backing for her Brexit strategy at Chequers, was timed for maximum impact, late on Sunday night.
As befits a man with SAS training, it caught his enemy - in this case, Number 10 - by surprise, allowing them no opportunity to mount an effective counter-attack.
Continuing the military analogy, Brexit ministers Steve Baker and Suella Braverman also went over the top, further weakening Theresa May's defences and leaving her exposed to further salvos from Tory Brexiteers in the hours ahead.
The contents of his resignation letter are particularly damaging for a Prime Minister struggling to sell her Brexit vision to a restive Conservative Party.
He says there have been "a significant number of occasions in the last year or so on which I have disagreed with the Number 10 policy line" on quitting the EU, not least the repeated delays to his cherished Brexit white paper, which is finally due to see the light of day this week.
The Chequers agreement, which would have ensured the softest Brexit Parliament and the EU could ever accept, was the straw which broke this particular camel's back.
"In my view the inevitable consequence of the proposed policies will be to make the supposed control by Parliament illusory rather than real," he said. "As I said at Cabinet, the “common rule book” policy hands control of large swathes of our economy to the EU and is certainly not returning control of our laws in any real sense. I am also unpersuaded that our negotiating approach will not just lead to further demands for concessions."
May's response, which displays all the warmth and empathy we have come to expect from her - ie none - merely re-states the main points of the Chequers agreement, and gives no indication that she is willing to further dilute her approach to appease DD's wing of the party.
So where does this leave Prime Minister, who is due to appear before the Conservative backbench 1922 Committee this evening?
She is undoubtedly weakened, but not yet fatally so. All eyes will now be on the other Cabinet Brexiteers, most notably Boris Johnson and Liam Fox, to see if they follow suit. If they do, a vote of confidence in her would be all-but inevitable as emboldened MPs send their letters to 1922 chairman Graham Brady demanding one.
The received wisdom up until now has been that May would have the numbers to comfortably survive, but that looks less certain now. Whether she would even want to take part is now open to question.
It is cliched, but the next few hours are crucial for the Conservative leader, as Number 10 desperately tries to quel the mounting rebellion. If they fail, her premiership will too. And even if she does limp on, how can she hope to get any withdrawal agreement she reaches with Brussels through Parliament in the autumn?
At the weekend, one senior Tory MP told me that despite his unhappiness with May, "an accidental leadership election would be madness".
They added: "I genuinely now fear Corbyn will be in Number 10 by this time next year."
It may be, the final reckoning, that the prospect of the Labour leader replacing her in Downing Street is what prevents the Conservatives from plunging the knife, rather than any real desire to see her crisis-strewn leadership continue.