Amber Rudd’s late night resignation from the post of Home Secretary deprives the government of one of its key figures, further destabilises Theresa May, upsets the balance of the cabinet’s deliberations on Brexit, complicates the Tory leadership race to come, and adds to the overwhelming sense that this is a crumbling administration.

Yep, as ministerial resignations go: this one has got the lot.

So much effort was poured into saving Rudd by Tory ministers and MPs in part because she is a popular figure among her colleagues. Not everyone agrees. There are some on the right of the Tory party at Westminster who cannot forgive her robust opposition to Brexit and liberal Tory views on other subjects. But for those of a more reasonable disposition, Rudd was one of the good people – that is decent, reasonable, humane and normal.

What Rudd was not, it turns out, was a deft administrator or alert player of the Whitehall game. The Windrush scandal was bad, but it would have been survivable without the bungling that followed it. On a basic question – were there targets or not for deporting illegal immigrants? – she was not across her department’s policy. Incidentally, there should be targets for deporting illegal immigrants. The Windrush citizens are not illegal immigrants. They… are… British… citizens.

But the real reason so much effort was put in by cabinet ministers, Number 10 and leading Tory MPs in a doomed attempt to save Rudd is that they know how serious the potential implications are.

Here are my initial thoughts on what it means:

1) Windrush becomes a May story, not a Rudd story. The line of responsibility on Windrush goes direct to Theresa May. She was Home Secretary from 2010 to 2016, and the policy happened on her watch. Already, the journalist who has led the way on this – Amelia Gentleman of The Guardian – is saying that the Windrush victims blame May. Rudd was cover for May, and and now that cover has been removed. May is badly exposed.

2) This government is more fragile than it looks. Brexit is approaching a parliamentary denouement on the question of whether the UK should stay in a customs union. Tempers are short, tensions are running high. Away from Rudd, the other major story this weekend was about the tension between the Brexit Secretary David Davis and Oliver Robbins, the PM’s lead civil servant on Brexit. Brexiteer ministers think that May has handed Robbins far too much control. In such a febrile atmosphere, there is a danger of miscommunication at best and walkouts and meltdowns at worst. In the face of this, a stronger Prime Minister would be banging the table, using persuasion, fear and guile to set the direction. Theresa May, it should be apparent by now, simply does not – cannot – operate that way. Britain finds itself at a crucial juncture trying to undertake something very difficult without a properly functioning Prime Minister as we traditionally understand it.

3) May has lost one of her main defenders. Whatever frustrations she had with May, Rudd rallied to her defence unprompted. Witness her forcing Boris to his feet to applaud during May’s coughing fit mid-speech at Conservative conference last year. Rudd had a practical sense that these squabbling boys had to be kicked up the backside.

4) Rudd’s departure alters the dynamics of the Tory leadership race. She was the potential compromise candidate to succeed May. Or she could have balanced a new Tory leadership ticket, as running mate and deputy Prime Minister to either an established Brexiteer such as Michael Gove or a next generation figure. Her colleagues are saying she will be back, but it is hardly a given. The leading liberal-Tory-legacy-Remain figure has had to resign from the cabinet over a scandal (Windrush) which will tarnish the Tories for years. It will take real skill and drive for her to recover.

5) Will Rudd become a leader of the soft-Brexit-hope-to-stop-Brexit  faction on the Tory backbenches? It would be out of character, and she presumably wants to return to government at some point, but resignation can make politicians shed their inhibitions, especially when they are presented with an opportunity to in public shoot down the idiocy of colleagues they have spent years being collegiate and polite about in public.

Lots more to come on all this, during what promises to be a fast-moving week at Westminster. Who will the next Home Secretary be? I shudder to think which ill-suited May loyalist could get it, unless more sensible voices intervene. Will Corbyn thank Labour moderate Yvette Cooper, whose smart questions did for Rudd? Unlikely. What’s the next explosion on Brexit going to be? Hold onto your hats.