Boris Johnson has made history by becoming the first sitting Prime Minister to be fined for breaking the law.
Rishi Sunak has also been fined for attending a lockdown party in Downing Street on 19 June 2020.
With any other Prime Minister, or Chancellor for that matter, this would have been considered an immediate resignation offence.
But Johnson has never acted as though normal rules and conventions apply to him.
And sure enough, he tonight dug in, resisting calls to resign despite paying the fixed penalty notice for a cake-fuelled birthday bash in the Cabinet room.
So what will happen now?
The early signs are Tory MPs are rallying round the PM to prevent a leadership vacuum at the height of the Ukraine war.
But whether he’ll survive to the next election is a very different question, as more fines, the Sue Gray report and local elections could all upset the balance.
Will Boris Johnson resign?
The Prime Minister has officially accepted he broke the Covid laws he set and expected the rest of the country to follow.
That offence alone would normally be considered a resignation issue.
He also stands accused of misleading MPs about the parties - a clear breach of the ministerial code - when he told the Commons he had been “repeatedly assured” there were no parties and no Covid rules were broken.
Anyone with honour would accept these two things meet the threshold for resignation.
But Mr Johnson, sacked twice for lying in his past, operates by a different set of standards.
While he accepted and paid the £50 fine, he denied lying to Parliament and refused calls to resign.
Will Rishi Sunak resign?
The Chancellor’s stock has tumbled in the last month after his lacklustre Spring Statement, botched photo opportunities and a furore over his wife’s tax affairs.
With his chances of reaching 10 Downing Street receding he could have considered an “honourable” resignation as an opportunity to step down from frontline politics and rebuild his career from backbenchers.
Or he could leave politics altogether to spend more time with his considerable fortune.
But such a move would heap pressure on Johnson to do the same.
Some Tory MPs may not forgive Sunak if his departure also caused the downfall of the Prime Minister and the implosion of the Government.
While there was an initial silence, the Chancellor, like his boss, eventually stood firm and tried to cling to his job. It's claimed he was warned not to resign for the reasons above.
Will Tory MPs trigger a leadership contest?
If Johnson refuses to resign the only people who can get rid of him are the 359 Conservative MPs.
If 54 of them submit letters of no confidence to the backbench 1922 Committee then it triggers a vote on the Prime Minister’s leadership.
If 180 MPs (half) then vote ‘no confidence’ in their leader it triggers a full leadership contest.
In February it was thought the 54-letter threshold was close to being met.
One senior Tory told the Mirror police action "would be terminal.” But the mood in the party has changed since the Russian invasion of Ukraine.
Many Tory MPs who had called for the PM to go, including Sir Roger Gale and Scottish leader Douglas Ross, argue it would be wrong to change the Prime Minister in the middle of an international crisis.
This conveniently forgets the fact that Neville Chamberlain was ousted during the Second World War.
The absence of an obvious successor is also working in his favour - as is the fact that Parliament is not sitting, making it harder for any plotters to organise.
Cabinet ministers have already swung behind the PM starting with Nadine Dorries. And Boris Johnson loyalist Michael Fabricant suggested the PM fight the penalty “just like a speeding fine”, adding: “The way it's been characterised, you'd think there had been pole dancers. And that certainly was not the case."
Will Parliament be recalled?
Labour and the Lib Dems called for a recall of Parliament from its Easter break so the PM can address the claims.
Mr Johnson had promised to update MPs when he got fined, but he has the final say over a recall, and seems unlikely to drag them back from their holidays.
Sky News reported the PM had been due to recall Parliament due to chemical weapons fears in Ukraine - but it was “now not possible” as it would be overtaken by Partygate.
Shadow Foreign Secretary David Lammy said: “If this is true, it shows how Boris Johnson’s ability to be Prime Minister has been crippled by his law-breaking. In the middle of Putin’s illegal war, we need a PM who can do everything necessary to support Ukraine.
"Not one who is hiding from Parliament to save his own skin.”
Parliament is due back anyway on April 19 and Boris Johnson could be expected to give a statement then.
Will there be a vote of no confidence?
A no confidence vote - instead of a Tory leadership vote - is the more official way of toppling the government of the day.
It involves all MPs of all stripes voting on a motion in the House of Commons that says they have "confidence" or "no confidence" in Her Majesty's Government.
But it has barely any prospect of success.
Anyone can do table a motion of no confidence, but for it to be guaranteed debating time, it usually has to be led by the Leader of the Opposition. Therefore the Lib Dems pushing for one is not enough.
Keir Starmer would be unlikely to table on because Boris Johnson still has an 80-odd majority. A no confidence vote would rally Tories round the PM suggesting he would easily win.
A Labour source said: “We want to hear from the Prime Minister at the earliest possible opportunity to give him the chance to correct his lies and tender his resignation.”
Will there be a Ministerial Code investigation?
The Ministerial Code notes there is an “overarching duty on Ministers to comply with the law”.
It also said ministers must uphold the duties of “transparency” and “honesty”.
Boris Johnson has admitted he broke the law and he is accused of being dishonest about it in the early days of the story.
That would suggest he could order an investigation into whether he broke the Ministerial Code, by ethics chief Lord Geidt.
However, it is up to the Prime Minister whether to order an investigation into himself - and the Prime Minister can overrule any finding that he broke the rules. There is no suggestion he will order such a probe.
Will he correct the record?
A snap YouGov poll of 2,464 people 75% believe the PM knowingly lied - with just 12% saying he did not.
He is accused of lying to Parliament when he said in December: "All guidance was followed completely in No10".
The Ministerial Code says it is “of paramount importance” that ministers give “accurate and truthful information” to the Commons and correct errors as soon as possible.
Yet the PM almost never corrects the record despite regularly being accused of misleading MPs.
And he has dug in over this too. Told his claim was a lie, he replied: “When I said that, I spoke in completely good faith.
“At the time that I was standing up for nine minutes in the Cabinet Room where I work every day, it didn't occur to me that I was [breaking the rules].”
How will Johnson try to wriggle off the hook?
Mr Johnson will do what he always does when in a bind: issue an insincere apology and then play for time in the expectation that something else will come along to distract the public’s attention, writes Jason Beattie.
The Downing Street defence will be that he was misled by staff when they gave him “repeated assurances” about the parties and he did not realise at the time he was breaking the law.
Admitting you did not realise you were at a party is not much of a defence but Johnson long ago decided that being branded a fool was a price worth paying if it meant he had a chance of survival.
If he starts to feel the heat, another option would be to submit himself to a vote of no confidence in the expectation he would probably win.
Will he try to appeal the fine in court?
No, he has paid the £50 fine. This means he has accepted he broke the law but will not get a criminal record.
The PM, his wife and Chancellor could all have contested the fines but only if they fight them in a magistrates' court.
If they lost in court they would get a criminal record. Magistrates would also hear an embarrassing to-and-fro of evidence in the public domain and the PM could have to give evidence in his own defence in a criminal setting.
Could police give Boris Johnson more Covid lockdown fines?
Yes. The Met Police appear to be working through their Partygate fines event by event, not person by person.
Scotland Yard and the Prime Minister have both made clear that more fines could follow as police trawl through more complicated events further down their to-do list.
Asked if more fines were coming his way Boris Johnson said: “If they are I'm sure that you will be the first to know, or amongst the very first to know."
After all that, will he be out of the woods?
Nope. Once the police investigation is over the second Sue Gray report into partygate will be published.
A first report by the Whitehall ethics chief in January blasted “failures of leadership” and said several lockdown parties - first revealed by the Mirror’s award-winning Political Editor Pippa Crerar - "should not have been allowed".
But she was barred from including many details as the police were investigating. Her second report is expected to present a fuller picture of what happened and could include damaging photographs and a more clear cut verdict on whether Johnson was complicit in the parties.
Meanwhile, Conservative MPs will be taking soundings from the constituency associations and monitoring their inboxes for the public reaction.
There is still a lot of resentment that, while people were unable to say farewell to lost loved ones or visit relatives in care homes, the occupants of No 10 were drinking suitcases of wine and singing along to Karaoke.
A lot could depend on the local elections on May 5. A backlash from voters could prompt Tory MPs to move against their leader.
