I was sitting in the Downing Street briefing room at the regular morning lobby on Tuesday 30 November, 2021.
Government scientist Dr Jenny Harries had just been on the radio, saying she thought that people should "be careful, not socialising when we don't particularly need to" in the weeks ahead.
But the PM's official spokesman didn't appear to agree, telling journalists that Harries "gives advice to the government, she is not the government".
I had been working on the No 10 party story for about six weeks, but immediately knew that now was the moment to get it over the line.
Covid was making headlines again, and we were in the run-up to the next Christmas. The public interest argument felt overwhelming.
The next morning, we published our splash with the headline " Boris party broke Covid rules " and the subhead "No 10 hosted boozy bash while millions endured strict lockdown".
We reported on two parties - one was the Christmas do on 18 December, 2020, at which up to 40 staff crammed "cheek by jowl" into a small room with wine and cheese, party games and a Secret Santa.
The second was a leaving do at which the PM made a speech and staff knocked back glasses of fizz.
Sources told me they were just two of "many gatherings" over lockdown and even suggested there were "always parties" in the flat Boris Johnson shares with his wife, adding: "Carrie's addicted to them". Those claims were firmly denied by Mrs Johnson.
But No 10 didn't deny our other claims - just insisted no rules were broken.
There's always a moment when you publish a story you think has the potential to have impact when you feel slightly sick.
Some in Westminster were sceptical. "It's a bubble story," one insider told me. "It was a year ago. Not sure it goes anywhere," another added.
At PMQs, I sat in the press gallery flanked by two of my team for moral support.
Labour leader Keir Starmer accused the PM of "taking the British public for fools".
Downing Street aides tied themselves in knots afterwards. The broadcasters went big with the story, but the papers were more cautious.
Yet one by one Government insiders sidled up to me, urging me to keep digging as there was a lot more to uncover.
After a week of obfuscation from the Government, the story exploded when ITV got hold of footage of Boris Johnson's own team joking about the No10 staff Christmas party.
It led to his senior aide Allegra Stratton delivering a tearful statement on her doorstep announcing she was quitting.
The PM - who said he was "sickened and furious" by the video - was forced to announce an inquiry by Cabinet Secretary Simon Case into the parties.
We kept plugging away at the story - revealing two gatherings in Downing Street and one at the DfE - but others were to follow.
These included pictures of the PM at a 'virtual' festive quiz at No 10 (even though most participants were in the building) with booze on his desk.
We also published an image of a Christmas bash held at CCHQ with a very dubious looking buffet.
All while the rest of the country was following lockdown rules.
The public hates double standards - and the PM's personal ratings started to plummet.
The next week I was glued to my phone just after 4am watching as the results of the North Shropshire by-election rolled in.
In a disastrous turn of events for the Tories, the Lib Dems took the previously true blue seat.
My phone started pinging shortly after, with Tory contacts lamenting how Boris Johnson had lost his way in recent weeks and their opponents claiming that 'partygate' had cut through on the ground.
More revelations followed - that the PM attended a May 2020 gathering in the Downing Street garden and, incredibly, that there was a party in Simon Case's own office, rendering his role overseeing the inquiry untenable.
Top civil servant Sue Gray took over and expanded the investigation - leaving some in No 10 quaking in their boots.
Although Mirror colleagues joke I'm never going to get invited to another party again, I do love a good knees-up.
But we were concerned about the Omicron variant ruining our Christmas so cancelled our social lives, worked from home and tested for Covid daily.
Luckily, the caution paid off and my family was able to head to Lancashire, then Scotland, for a week.
After Christmas, the list of rule-busting lockdown parties continued to grow.
The PM's former top aide Dominic Cummings published a blog in which he claimed the PM and dozens of staff held a BYOB party in the No 10 garden.
A few days later an email - sent by the PM's top civil servant aide - leaked which invited 200 staff to "make the most of the lovely weather " and join the celebrations. Tables were laden with booze and snacks as Mr Johnson, his wife Carrie and around 30 No 10 aides partied in the sunshine.
More allegations followed - we broke stories about 'Wine Time Fridays', No 10 staff buying a drinks fridge, suitcases of booze being rolled into No 10.
There was especially shocking revelations that aides downed booze at two leaving parties the night before the Queen sat alone at Prince Philip ’s funeral.
It didn't stop there.
A tale about a lockdown birthday party organised by the PM's wife in the Cabinet room descended into a bizarre row about being ambushed by a cake.
We later revealed that there were pictures of the PM toasting with a can of Estrella beer - taken by the taxpayer funded No 10 photographer.
And as more stories came out, so Mr Johnson's responses developed, from "all the guidance was followed at all times" to "I certainly broke no rules".
As Tory MPs' email inboxes filled up with missives from angry constituents, the PM's position began to look more precarious.
Rebellious red wall Tory MPs plotted his downfall, submitting letters of no confidence to try to trigger a leadership contest. One told me: "His time has gone".
But the 'Pork Pie Plot' fizzled out after No 10 launched a tough operation sending out the PM's enforcers to get them back in line.
A week later, on January 25, the Met Police dropped a bombshell and announced it would investigate Downing Street lockdown breaches.
They asked Sue Gray to put her inquiry on hold - but not before she put out a devastating interim report.
She revealed she was looking at a dozen events - including six himself PM attended.
And she slammed failures of leadership and said lockdown parties were "difficult to justify" while the rest of the country followed the rules.
Months of speculation and frustration followed as we tried to piece together what was happening with the distinctly opaque police inquiry.
The delay gave the PM time to shore up his position with angry MPs - and his renewed focus on Ukraine left may feeling now was not the time to oust him.
Scotland Yard issued their first fixed penalty notices in late March - eventually reaching a total of 126 fines issued for 83 people at events on eight days.
Mr Johnson was issued a single fine - to the surprise of many - for his surprise No 10 birthday party. He apologised saying he hadn't realised he'd broken rules.
Rishi Sunak was also fined, the final nail in the coffin of the millionaire Chancellor's dreams of taking over at No 10 after a row over his wife's tax arrangements.
Eventually, Scotland Yard announced that their four-month inquiry was over and the PM would be issued no more fines.
The greased piglet - so-called because of his ability to wriggle out of trouble - had escaped again.
No 10 insiders tell us the PM doesn't want to "spend another second" on Partygate and wants to move on.
But the damage to Boris Johnson's reputation is done.
While the majority of Tory MPs haven't sacked him, they aren't backing him either, and they remain jittery.
The Commons privileges committee still has to investigate whether he deliberately misled Parliament.
And the most important judge of all - the public - made up their minds long ago with polls showing the majority of voters believe he lied.
When the PM addressed Tory MPs last night, he told them the Partygate scandal had been like "having a mirror held up to the inner workings of No 10" which he added was "always a bit painful".
He can rest assured, this Mirror will continue to reflect what is going on behind the famous black door of Downing Street - painful for the PM or not.
