Desperate Boris Johnson has pleaded with MPs not to find him guilty of contempt of Parliament - which could end his career in the Commons.
The shameless former Prime Minister today tried to deflect blame for the scandal onto advisors, and launched an astonishing attack on Dominic Cummings - who he said had "every motive to lie".
In an often bad-tempered face-off with members of the Privileges Committee, he was accused of using a "deflection mechanism" and told it was "obvious" that lockdown gatherings broke rules.
Mr Johnson - who was forced to quit last summer after another scandal, the appointment of Chris Pincher - claimed that a leaving do in November 2020 was a "necessary" work meeting.
He also hinted he would not accept a guilty verdict.
Here we look at some of the key moments from an often tetchy afternoon.
No 'drill sergeant' or 'electrified forcefield' to enforce social distancing in No10
Social distancing was not "necessary or possible" in No10 due to the working conditions in the "cramped" 18th Century townhouse, Mr Johnson said.
The former Prime Minister said his insistence Covid guidance was followed was based on "my understanding of the rules and the guidance".
But he added: "That did not mean that I believed that social distancing was complied with perfectly.
“That is because I and others in the building did not think it necessary or possible to have a two-metre, or one-metre after June 24 2020, electrified forcefield around every human being.
"Indeed that is emphatically not what the guidance prescribes.”
While attempts were made to respect social distancing, including giving people "as wide a berth as we could”, he claimed: “It would have been impossible to have a drill sergeant measuring the distancing between us all hours of the day and night."
Person who told me no rules were broken asked me not to give her name
Mr Johnson told the committee - and said in his written evidence - that he had been told by officials in a morning meeting who had advised him that no rules had been broken.
Pressed to name the individuals, the former PM said: "I can't name these people... I don't know if I can."
He then said: "There's at least one advisor who asked not to be named."
Tory MP Alberto Costa told him: "Why did you tell the House of Commons that you'd received repeated assurances that no rules had been broken when you knew that wasn't the case because you knew what the rules were.
"You were at gatherings that breached the rules and the breaches of the rules would have been obvious to you at the time. Some might say your reliance on the purported assurances you received are a deflection mechanism to prevent having to answer questions about your knowledge of the gatherings."
Mr Johnson dismissed this as a "ridiculous" assessment.
Cabinet Secretary Simon Case has told the inquiry that he was not aware of any officials giving Mr Johnson that assurance.
Jack Doyle, who was Mr Johnson's communications chief when the partygate story broke, said he did not tell Mr Johnson that all coronavirus guidance was followed.
And former principal private secretary Martin Reynolds said he warned against claiming that all rules had been followed before Mr Johnson issued a denial to Parliament.
My birthday cake stayed in a Tupperware box and was eaten by my secretaries
Boris Johnson repeatedly stressed he was only fined for one event: his surprise birthday party.
"A number of officials came in to wish me a happy birthday,” he told the committee.
“No one sang, the famous Union Jack cake remained in its Tupperware box, unnoticed by me, and was later discovered and eaten by my private secretaries."
A "slightly exaggerated" version of the event was briefed to The Times "with singing and cake eating" and yet nothing untoward was detected "either by the reporter or by millions of eagle-eyed readers", he claimed.
That meant that when he addressed MPs "it did not for one second occur to me that this event, the one event for which I was fined, would later be found to be somehow against the rules".
Boozy leaving do 'necessary' after 'acrimonious' departure of top aides
Spin chief Lee Cain’s leaving do - where Mr Johnson gave a speech - was the subject of intense questioning.
The communications director’s exit - along with the departure of No10 top aide Dominic Cummings - was triggered by a power struggle with Mr Johnson’s then fiancee Carrie.
The then Prime Minister insisted he needed to be at the November 13, 2020 leaving bash to “steady the ship” and “show there was no rancour”.
"This meeting happened on an impromptu basis, it had to happen,” he said.
"It was necessary because two senior members of staff, the effective chief of staff and director of communications, had both left the building, or were about to leave the building in pretty acrimonious circumstances - or what were potentially acrimonious circumstances.
"It was important for me to be there and to give reassurance."
Whole thing sounded like a 'Daily Mirror try-on'
Mr Johnson said that when No10 was initially contacted about a Christmas party in 2020, he dismissed it as a "Daily Mirror try-on".
He told the committee: "On the evening in question, November 30 2021, I was dealing with the emergence of the Omicron variant and the growing clamour for restrictions on another Christmas.
"I could not drop what I was doing, get up and institute a personal investigation into what sounded like a Daily Mirror try-on about an event that was now almost a year old.
"I had to rely on and was fully entitled to rely on what I was told by my senior trusted advisers. The Government would be paralysed if minsters were not able to do so."
People passed each other drinks but they didn't pass each other pens
The ex-PM made a string of bizarre claims about the social distancing in No10 - but then admitted people still passed each other drinks.
"We avoided physical contact. We didn't for instance, as the guidance said, we didn't touch each others pens. We didn't pass stuff to each other if we could possible avoid it. I would not wish to say that was perfectly implemented."
He admitted people were "of course" passing drinks to each other in the picture.
But he added: "This is guidance. I'm not going to pretend it was enforced rigidly but that's explicitly what the guidance provides for."
It was "regular, I'm afraid, for people to drink on Fridays"
The Prime Minister said that Friday drinking was "regular" inside No10.
He blamed former communications chief Jack Doyle for convincing him that boozy bashes were not illegal.
Mr Johnson told the committee: “He told me that it was within the rules, he said that people were sitting at their desks - drinking, admittedly.
"But that was not banned under either the rules of the guidance.”
Rishi Sunak would have known about it too
Mr Johnson made it clear that if he was in the wrong, senior officials and figures including Rishi Sunak would have been equally aware what was going on.
He claimed it was "nonsense" that he would have known he was breaking rules, and claimed it was "staggeringly implausible" that an official photographer would have been asked to photo an "illicit" event.
He continued: "If we had an event that was unauthorised, why would we have it on Zoom?"
"If it was obvious that these events were contrary to the rules it must have been unquestionably obvious to some of the most senior officials in the country and it must have been obvious to others in the building, including the current Prime Minister," he said.
He said that accusing him of lying meant civil servants and politicians were being accused of lying.
Dominic Cummings 'has every motive to lie'
Moments after dragging Mr Sunak into the debacle, Mr Johnson set his sights on former chief advisor Dominic Cummings.
He added that a claim by Mr Cummings, to have raised concerns with the then prime minister was "unsupported by any documentary evidence" and "plainly cannot be relied on".
"He has every motive to lie," Mr Johnson claimed.
I respect committee, but finding me guilty wouldn't be fair
Mr Johnson was asked by fellow Tory Charles Walker what he made of other members of their party describing the committee as a "kangaroo court" - a term used by former Culture Secretary Nadine Dorries last year.
"If this committee were to find me in contempt of Parliament I think that would be unfair and wrong."
He claimed, however, to respect the committee - but hinted he would only accept his verdict if he's cleared.
"That's why I've come here, out of respect for this committee, out of respect for Parliament, I don't believe that you can find me guilty of willfully misleading Parliament."
