The Cabinet Office has admitted a quiz was held in the department on December 17 2020, causing Cabinet Secretary Simon Case to recuse himself from leading an investigation into gatherings across Whitehall.

Sue Gray, second permanent secretary at the Department for Levelling Up, Housing and Communities, will now lead the probe, which could be expanded to include any relevant allegation.

Here is a list of what has been alleged.

– May 15 2020: Downing Street garden party

Boris Johnson spent around 15 minutes with staff in the Downing Street garden, telling one aide they deserved a drink for “beating back” coronavirus, the Guardian and Independent reported.

Sources said around 20 staff drank wine and spirits and ate pizza following a press conference at which then health secretary Matt Hancock told the British public to stay at home “as much as is possible”.

A No 10 spokesman said: “On May 15 2020 the Prime Minister held a series of meetings throughout the afternoon, including briefly with the then health and care secretary and his team in the garden following a press conference.

“The Prime Minister went to his residence shortly after 7pm.

“A small number of staff required to be in work remained in the Downing Street garden for part of the afternoon and evening.”

– November 13: A leaving party for senior aide

According to reports at the time, Mr Johnson gave a leaving speech for Lee Cain, his departing director of communications and close ally of former chief Downing Street adviser Dominic Cummings.

England was in a month-long lockdown at the time when meeting people from other households indoors was banned, except for work purposes.

– November 13: Johnsons’ flat party

There are allegations that the Prime Minister’s then fiancee hosted parties in their flat, in what would also have been a breach of Covid guidance, with one such event said to have taken place on November 13, the night Mr Cummings departed No 10.

Mr Cummings, who has become a vocal critic of Mr Johnson and his now wife, Carrie Johnson, since his exit from No 10, has called for the investigation into possible rule breaches to include the so-called “flat party”.

A spokesman for Mrs Johnson has called the claim “total nonsense”.

– November 27: A second staff leaving do

The Mirror, in the newspaper’s original report breaking the story, said that, while the Prime Minister did not attend the alleged No 10 flat party in December, he did give a farewell speech to an aide at the end of November, while the lockdown in England was still in place.

Other reports have said the leaving do was for Cleo Watson, a senior Downing Street aide and ally of Mr Cummings.

The event forms part of the investigation which was ordered by the Prime Minister.– December 10: Department for Education party

According to The Mirror, former education secretary Gavin Williamson threw a party and delivered a short speech at an event organised at his department’s Whitehall headquarters, which took place while London was in Tier 2, which banned any social mixing between households.

The DfE confirmed the social event happened but acknowledged that “it would have been better not to have gathered in this way at that particular time”.

This event is also covered by the investigation.

– December 14: Party featuring Tory London mayoral candidate Shaun Bailey and staff

Shaun Bailey apologised “unreservedly” for attending the gathering at Conservative Campaign Headquarters (CCHQ) organised by staff on his campaign team.

“It was a serious error of judgment at a time when Londoners were making immense sacrifices to keep us all safe and I regret it wholeheartedly,” he tweeted.

He quit his role chairing the London Assembly’s police and crime committee after the Daily Mirror published a picture showing him at the gathering.

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: Downing Street quiz

The Prime Minister appeared on contestants’ screens at the quiz but insisted he broke no rules.

An image published by the Sunday Mirror shows the Prime Minister flanked by colleagues, one draped in tinsel and another wearing a Santa hat, in No 10.

Downing Street admitted Mr Johnson “briefly” attended the quiz after the photographic evidence emerged but insisted it was a virtual event.

However the newspaper quoted a source who said many staff were huddled by computers in their Downing Street offices, conferring on questions and drinking alcohol while the quiz was taking place.

The quiz will be examined as part of the investigation.

– December 16: Department for Transport party

The Daily Mirror reported senior civil servants were “boozing and dancing” at the event, allegedly planned by staff from Transport Secretary Grant Shapps’ office.

A DfT spokesman said: “The Secretary of State wasn’t involved in any gathering at the department.

“Fewer than a dozen staff who were working in the office had a low-key, socially distanced, gathering in the large open-plan office after work on December 16, where food and drink was consumed.

“We recognise this was inappropriate and apologise for the error of judgment.

– December 17: Cabinet Office “Christmas party!”

A number of outlets reported that a gathering was held in the Cabinet Office, Mr Case’s own department, on December 17.

The Times reported that Mr Case attended the party in room 103 of the Cabinet Office, that it had been organised by a private secretary in Mr Case’s team, and that it was included in digital calendars as “Christmas party!”.

The Cabinet Office confirmed a quiz took place, but a spokesperson said: “The Cabinet Secretary played no part in the event, but walked through the team’s office on the way to his own office.

“No outside guests or other staff were invited or present.

“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.”

– December 18: Christmas party at Downing Street

The claim at the centre of the rule-breaking allegations is that a party was held for Downing Street staff on December 18.

Officials and advisers reportedly made speeches, enjoyed a cheese board, drank together and exchanged Secret Santa gifts, although the Prime Minister is not thought to have attended.

Mr Johnson’s spokeswoman Allegra Stratton quit after being filmed joking about it with fellow aides at a mock press conference.

The event is at the heart of the investigation which will now be led by Ms Gray.