A crisis engulfed Downing Street at the end of 2021 after ITV News released leaked footage of senior staff laughing about a Christmas party in Number 10, alleged to have happened just days before.
That event on December 18 is the subject of an investigation ordered by Boris Johnson (though he hasn't actually admitted the party took place) and his former press secretary resigned over the video.
Cabinet Secretary Simon Case was tasked by the PM with heading up the No 10 party inquiry, but has since stepped down following accusations that his department's office held its own gathering.
Sue Gray, second permanent secretary at the Department for Levelling Up, Housing and Communities, is now leading the probe, which could be expanded to include any relevant allegation.
A growing list of other parties are alleged to have happened, some confirmed to have taken place during 2020 and 2021 when various Covid restrictions were in place.
The government has confirmed some of those events will also be looked into by the investigation. Here's a list of the parties in order of when they are alleged to have happened:
April 16: No10 parties held on eve of Prince Philip's funeral
Two Downing Street parties are alleged to have been held the night before the Duke of Edinburgh's funeral in April last year, while the country was in a period of national mourning and mass indoor social mixing was still barred, The Telegraph reports.
It was said that advisers and civil servants gathered after work for two separate events to mark the departure of James Slack, Boris Johnson’s former director of communications, and one of the PM’s personal photographers.
The two parties later merged together and had 30 people in attendance, with witnesses saying that alcohol was drunk and guests danced to music.
A source, who attended the April 16 party, told ITV News UK Editor Paul Brand that descriptions of the parties are “incredibly accurate” and more than one staff member got merry enough to use Boris Johnson's son Wilf's swing.
Mr Slack admitted a leaving do- at which he gave a speech to mark his departure from No10 to become deputy editor-in-chief of The Sun newspaper- was held in his honour and apologised.
May 15: PM "joined" Number 10 garden pizza party
The outlets reported that the PM was present for 15 minutes at the gathering following a Covid press conference on May 15, at which then Health Secretary Matt Hancock told the British public to stay at home “as much as is possible”.
Mr Hancock stressed the rules in force meant “you can meet one other person from outside your household in an outdoor, public place” as long as you kept two metres apart.
But sources alleged that some 20 staff members drank wine and spirits and ate pizza following the press conference, with Mr Johnson said to have told one aide that they deserved a drink for “beating back” coronavirus.
Some aides reportedly carried on drinking into the evening, although there was no suggestion Mr Johnson or Mr Hancock had any alcohol or stayed late.
In response to the claims, Downing Street said the prime minister held a "series of meetings throughout the afternoon" and “briefly” met Mr Hancock and his team in the garden, which was “regularly” used for work meetings during the summer months.
“A small number of staff required to be in work remained in the Downing Street garden for part of the afternoon and evening,” added a No 10 spokesman.
May 20: PM and wife join BYOB No 10 garden party
The prime minister and his wife Carrie were among 40 members of staff who gathered in the No 10 garden that evening "to make the most of the lovely weather", enjoying picnic food and drinking, ITV News understands.
The PM's Principal Private Secretary Martin Reynolds sent an email - shared exclusively with ITV News - to more than a hundred Downing Street employees inviting them to the party on May 20, 2020.
At the time, the rest of the country was banned from meeting more than one other person from another household outdoors. They could only do so in a public place while remaining two metres apart.
Mr Reynolds wrote to staff: "After what has been an incredibly busy period it would be nice to make the most of the lovely weather and have some socially distanced drinks in the No10 garden this evening.
"Please join us from 6pm and bring your own booze!"
Less than an hour before the drinks, then Culture Secretary Oliver Dowden had reminded the rest of England at the daily No 10 press conference that they must only meet in pairs outdoors.
Downing Street told ITV News they would not comment on the story due to the Sue Gray inquiry.
November 13: Boris Johnson's "flat party"
In the fallout from the leaked Downing Street video, the prime minister's former top aide Dominic Cummings (himself involved in a Covid rules scandal) accused Number 10 of hosting a party on Friday November 13 - the night he gave up his government role.
The former chief advisor said the investigation of the December 18 gathering should also look into "the flat party on Fri 13 Nov, the other flat parties, and the flat's 'bubble' policy".
The latter may be in reference allegations Mr Johnson and wife Carrie broke lockdown rules to have a friend over on Christmas Day.
A spokesman for Mrs Johnson has called Mr Cummings' claim “total nonsense”.
November 25: Treasury drinks
The Times reported that two dozen Treasury officials held a "drinks party" in their office to celebrate the autumn spending review.
Chancellor Rishi Sunak was not at the event, the paper said, adding that it understood he was not aware of it at the time.
A Treasury spokesman said: "A number of HMT staff came into the office to work on the Spending Review 2020. We have been made aware that a small number of staff had impromptu drinks around their desks after the event. “The Treasury did not organise an in-person departmental party last Christmas.”
November 27: Staff leaving do
It has been confirmed the PM did not attend the December 18 party but there are calls for an investigation into a leaving do on November 27 which he allegedly gave a speech at - a time when England's lockdown was in place.
Sources have told ITV News Political Editor Robert Peston the PM "ducked in" to an impromptu get together when Cleo Watson left her job as an important aide.
December 10: Department for Education party
Former education secretary Gavin Williamson threw a gathering for his department on December 10, while London was in Tier 2 which banned social mixing between households.
The Department for Education did not deny Covid rules had been broken and told The Mirror "it would have been better" not to have had the event.
Current education secretary Nadhim Zahawi told ITV's Peston he was sorry staff had "gathered together" but denied it was a party, saying there was "no outside catering or outside people coming into the building".
December 14: Shaun Bailey mayoral campaign party
A party was confirmed to have been held at the Tory Party's campaign headquarters, organised by Shaun Bailey’s mayoral campaign on December 14.
This falls under the remit of the Conservative Party, rather than the government event and won't be included in the Cabinet Secretary's investigation.
According to the Times, the “raucous” party took place and was attended by No 10 aides and featured dancing and wine-drinking into the early hours.
Mr Bailey apologised “unreservedly” for attending and quit his role chairing the London Assembly’s police and crime committee after the Daily Mirror published a picture showing him at the gathering.
A Conservative Party spokesperson said "formal disciplinary action was taken against" four organisers.
The Metropolitan Police said officers will be making contact with two people who attended “in relation to alleged breaches of the Health Protection (Coronavirus, Restrictions) Regulations”.
December 15: Number 10 Christmas quiz
The prime minister has been accused of breaking Covid rules last year after a picture emerged of him allegedly hosting a quiz via video link at Number 10.
The Mirror reported the image is from December 15 2020 and claim it shows Boris Johnson flanked by two members of his top team - one draped in tinsel and another wearing a Santa hat - as he hosts a Christmas quiz in No 10.
Number 10 spokesperson said: "This was a virtual quiz. Downing Street staff were often required to be in the office to work on the pandemic response so those who were in the office for work may have attended virtually from their desks.
"The Prime Minister briefly took part virtually in a quiz to thank staff for their hard work throughout the year."
The quiz will be examined as part of the investigation.
December 16: Department for Transport Christmas party
The department apologised for staff holding the Christmas gathering during last year's lockdown, saying it was "inappropriate" and an "error of judgment".
A spokesman for Transport Secretary Grant Shapps said he had "absolutely no idea" about the event.
December 17: Cabinet Office "Christmas Party"
The Cabinet Office confirmed a "virtual quiz" took place in Cabinet Secretary Simon Case's department on December 17.
A source confirmed to ITV News that six people who were in the office that day took part in person, in a socially distanced manner, while most attendees dialled in remotely from home.
However, the source said Mr Case did not actively take part but acknowledged staff. The source added he knew the gathering was happening as he had to walk past the group in order to get to his private office.
The Cabinet Office said in a statement that a "small number of people who had been working in the office throughout the pandemic and on duty that day, took part from their desks".
“This lasted for an hour and drinks and snacks were bought by those attending. He also spoke briefly to staff in the office before leaving," it added.
According to Guido Fawkes, a second event in Mr Case's department saw staff drinking together in the office before heading out elsewhere in December.
Following the accusations, Mr Case stepped down as head of the inquiry into the alleged Downing Street parties and has been replaced by second permanent secretary in the Cabinet Office Sue Gray.
December 17: Cabinet Office leaving do
A leaving party took place in the Cabinet Office on that same evening during the December 2020 Christmas lockdown, an official has admitted.
The event was a leaving do for Kate Josephs, who until then had been responsible for drawing up Covid restrictions as boss of the Cabinet Office's Covid Taskforce.
Ms Josephs, who is now CEO of Sheffield City Council, confirmed the party took place on Twitter and said she is "truly sorry".
She wrote: "On the evening of 17 December, I gathered with colleagues that were at work that day, with drinks, in our office in the Cabinet Office, to mark my leaving the Civil Service.
"I am truly sorry that I did this and for the anger that people will feel as a result. I apologise unreservedly."
The party is understood to have been separate to the alleged Christmas party held in the Cabinet Office on the same day, and took place just 24 hours before the No10 "cheese and wine" party is alleged to have happened.
December 18: Downing Street Christmas party
The PM apologised for the video, obtained by ITV News, of senior Downing Street staff laughing in the days after the December 18 party is alleged to have happened.
An investigation is underway into the party - though the government is yet to admit the party actually happened, with Mr Johnson saying he was "furious" over the footage.
Watch the leaked video, obtained by ITV News, showing senior Downing Street staff joking about the December 18 party - days after it's alleged to have taken place
Staff can be heard laughing and making references to “cheese and wine”, while Mr Johnson’s then spokesperson Allegra Stratton remarked there was “definitely no social distancing.”
The recording is of a rehearsal on December 22 for Downing Street's proposed daily TV media briefings, which Ms Stratton was set to front before they were later abandoned.