On his own narrow terms, Johnson was smart to use the Sue Gray report and the Metropolitan Police investigations to buy time. Not that he had much option. Something might turn up, he seems to have wagered, like Putin starting a war or an economic crisis. So it transpired. He might even buy more time now, by taking the ticket to appeal at a magistrates’ court. Entirely cynical, but a typical attempt to play the rules. Every day still in office is another day of options staying open. Besides, a lot of his allies will just argue that this is the wrong time for a leadership change. Also – fortunately for Johnson – his most dangerous rival, Rishi Sunak, has been discredited – not least by getting his very own Covid fine. Johnson can’t quit now, surely?

Well, let’s be clear about this point. He could. Mariupol won’t fall. Kyiv won’t surrender. There will be no victory parade in Red Square just because the British prime minister is about to be replaced. We’ve changed PMs in wartime before, in both world wars – wars of national survival, too – and Zelensky will be fine with our next leader. The French, after all, are holding a presidential election, with the prospect of a much more radical change at the top. Whoever follows Johnson won’t change the policy on Ukraine. The easiest and best option would be to replace Johnson with the likes of Liz Truss or Ben Wallace. The cabinet could, and should, prevail on Johnson to quit, and install a new premier, either temporarily or permanently, and in time for the local elections – along with a new chancellor, the removal of duffers such as Rees-Mogg, Patel and Dorries, and a fresh start.

At the moment, despite what his fans say, Johnson is an electoral liability: the first prime minister to be found guilty of a criminal offence in office; a man who can be called a criminal (assuming he doesn’t get acquitted on appeal) without fear of a libel suit. A man whom many accuse of lying to parliament, leading a government that is insensitive to the cost of living crisis and with more than a whiff of decay about it.

It feels like Johnson’s time is up. He’s run out of road.

But that moment passed. The most significant change was that Johnson and the Conservative Party started to recover in the opinion polls. Conservative MPs were contemplating a change of leader mainly because they thought Johnson had become an irredeemable vote-loser; but it became obvious quite quickly that Labour wasn’t nearly far enough ahead to maintain the necessary level of panic.

Then events started to crowd in on history. Vladimir Putin invaded Ukraine; the chancellor delivered a mini-budget that went down badly; and then he was engulfed in controversy about his wife’s non-dom status. Johnson is up; Sunak is down; and what is more, Sunak has received a penalty notice as well. The prime minister may well receive more than one notice. I thought the birthday cake gathering was one of the lesser charges, and that Sunak’s defence for that was a good one – that he turned up for an important meeting. But Johnson was at several gatherings where there seemed to be less of an excuse.

If the prime minister thinks he can try to avoid disclosing how many penalty notices he receives, he will be put right by his advisers: it won’t be possible. Too many people will know. Even so, he will survive. In the meantime, the opposition will overreach itself, claiming that Johnson and Sunak misled parliament when they said no rules had been broken. But they cannot claim that the prime minister and chancellor did so “knowingly”, which is the constitutional tripwire. And ultimately, whether the law was broken remains a matter of opinion: the police say they think it was; Johnson and Sunak may insist that in their view they were within the law, but that they are paying the penalty because they don’t want to go to court.

The brutal bottom line is that Conservative MPs are the ultimate judge and jury in the prime minister’s case: if 54 of them demand a vote of confidence in Johnson, it must be held, and if 181 of the total of 360 vote against him, he must go. That is not going to happen. Johnson is going to survive.

The more interesting question is whether Sunak uses this as the moment to quit. There has been a lot of commentary in recent days about how he will just pack up and go to California if things get too rough for him here. I think that is a misreading of him. Things don’t look great for him, but the one thing that that last few days have shown is that politics changes fast. In a year’s time, Sunak may be a contender again, riding the tide of economic recovery.