Boris Johnson has until tonight to return his Metropolitan Police Partygate questionnaire.
The Prime Minister was issued with the form last Friday by Scotland Yard, who are investigating 12 parties in Downing Street and Whitehall during lockdown.
He has been consulting lawyers over his response - and is expected to resist any attempts to oust him from No10 if he is slapped with a fine.
If he is fined, the consequences will begin to spiral - from a second Sue Gray report to a possible Tory leadership challenge.
But any decision by Scotland Yard is still thought to be weeks away, and it may leave more questions than it answers.
No 10 has said it will say if Mr Johnson is hit with a fixed penalty notice, but the identity of any other No10 staff who are fined could be kept secret.
Meanwhile the 300 photos which civil servant Sue Gray collected and passed to police are unlikely to see the light of day - unless they get leaked.
So what's next for Boris Johnson - and can he survive what’s coming?
Get his excuses in
The PM has been consulting with his lawyers on how to face down the police investigation - which could see him receive a fixed penalty notice if he is found to have broken his Covid regulations.
Mr Johnson has already admitted to attending some of the parties in question but he is getting his excuses in to avoid being fined.
His defence is expected to focus on the "unique" situation of Downing Street being his workplace and his home - which could give him cover for being in the No 10 garden, for example.
Mr Johnson will also try to argue he attended some events as part of the working day, such as leaving dos.
But he was widely mocked when told MPs last month that he believed a BYOB bash in the Downing Street garden was a "work event".
The PM’s lawyers reportedly now believe the relevant test is whether he returned to “proper work” after the gatherings.
But barrister Adam Wagner, who analyses Covid lockdown laws, said this was “irrelevant”.
Mr Johnson is apparently expected to argue that he was surprised by the birthday gathering and that he was working in his flat on the night of the November 2020 party.
Wait for the Met Police's Partygate verdict
Scotland Yard have contacted more than 50 people about lockdown-flouting parties, with those affected given seven days to respond.
It is unclear how long it will take the Met to go through the response, as well as the tranches of evidence handed over by top civil servant Sue Gray.
The results of their inquiry could take weeks - or indeed longer - to emerge.
If the Prime Minister is fined by police then he will be under massive pressure from the public and his own MPs.
Many Tories are waiting for the results of the police probe before they decide whether to call for a no confidence vote.
If he is not fined, the inquiry could be branded a whitewash and risk angering people who were fined for breaking Covid rules.
Sue Gray’s second report
Top civil servant Sue Gray was tasked with investigating the Partygate allegations but her report has been put on ice while the police investigate.
Ms Gray was forced to publish only a short update last month after the Met Police U-turned on its refusal to investigate reports of rule-breaking gatherings.
Her inquiry examined 16 events, including a handful that the police decided not to investigate.
This could still be highly damaging for the PM, even if he isn't fined by the police.
Ms Gray was highly critical in her update, warning that some of the events should not have taken place and amount to a "serious failure" of standards.
Her full report is likely to be even more robust.
Brace for more photos to be leaked
Unfortunately for Boris Johnson, a picture is worth a thousand words.
The Met Police revealed they had been handed 300 images relating to their Partygate probe by Sue Gray, which are thought to include CCTV stills.
Ms Gray is not expected to publish the images as part of her second report and the Cabinet Office has asked the police not to release the pictures.
But the Liberal Democrats are mounting a Commons bid to force publication of the full report, including the pictures.
If they don't succeed, there is always a chance that pictures could be leaked to the media.
The Mirror understands that there is a photo showing the PM with a beer, which could prove difficult for him to explain away.
Ex-No 10 aide Dominic Cummings, who has declared war on his former boss, has warned publicly that there are damaging pictures out there.
Steel himself for a Tory leadership challenge
If the PM is fined or Sue Gray's report is explosive then the Prime Minister could face a no confidence vote.
Tory MPs can trigger a vote in their leader if 15% write to the chairman of the backbench 1922 Committee.
There are 360 MPs with the Tory whip, so 54 of them need to send in their letters.
If the threshold is reached, Mr Johnson must receive support from 50% of MPs to survive.
If he wins then he is safe from being challenged for a year. If he loses, then a leadership contest will be held.
Chancellor Rishi Sunak and Foreign Secretary Liz Truss are regarded as frontrunners for the top job but plenty of others could throw their hats into the ring.
Suffer the consequences in the polls
Any fine could lower the Prime Minister further in the eyes of the voting public. This could trigger a leadership challenge or, if not, an election drubbing.
Latest Ipsos polling reveals the damage already inflicted on Mr Johnson’s premiership by the Partygate scandal, first exposed by the Mirror.
Fifty-four percent of voters think he has done a bad job as Prime Minister, while just 29% claim he has done a good job.
Some 56% back Conservative MPs triggering a vote of no confidence in his leadership by submitting letters to the party’s 1922 Committee.
Ipsos’ director of politics Keiran Pedley said: “The data continues to show Boris Johnson’s personal poll ratings weakening, with a majority of Britons now saying he has done a bad job as Prime Minister and a majority supporting the concept of Conservative MPs triggering a vote of no-confidence in his leadership.
“What happens next will likely be decided by events, as police investigations draw to close and other items move up the news agenda.”
Ipsos quizzed 2,038 adults online between last week.
Try to get through the May elections
Voters will head to the polls in May across the UK to elect a mix of local councils and mayors.
It will be the first electoral test since the Partygate row - and a chance for politicians to see how the scandal has played out with voters.
While local elections can hinge on issues like bin collections, potholes and parks, all of the parties will be watching keenly for any sign that the row is helping - or hampering - them on the ground.
See if he can hang on for the general election
The real test for Boris Johnson will be the next general election - if Tory MPs keep him in power until then.
Voters are not due to go to the polls until 2024 but the PM could call it early after the Tories pushed to repeal the Fixed Term Parliament Act which provides a set gap between elections.
Mr Johnson might decide to limp on through to 2024 in the hope that he can right the ship or he could be ousted before that happens if Tories think he will cost them their seats.
It is worth remembering that John Major won a leadership challenge in 1995 but he was roundly defeated in 1997 in Tony Blair's landslide victory
