British Prime Minister Boris Johnson is under pressure to resign after admitting he attended a garden party at his Downing Street residence in May 2020, in breach of his government’s coronavirus lockdown rules.

Johnson’s admission and apology on Wednesday marked the latest and most-high profile scandal yet in a string of controversies over allegedly rule-breaking gatherings involving the Conservative Party leader, his staff and other senior figures since the pandemic began.

Several such events were allegedly held throughout 2020 while the UK struggled to confront a soaring virus caseload that caused tens of thousands of deaths and precipitated a historic economic downturn as well as widespread gloom amid the strict curbs imposed on Britons’ daily lives.

The alleged parties, all of which took place at various locations in the capital, London, have only recently come to light amid a flurry of reporting on them from British media outlets since the beginning of last month.

They are now being investigated by senior civil servant Sue Gray, who has been tasked by Johnson’s government with leading an inquiry into whether gatherings were held in contravention of COVID-19 restrictions.

Here’s a timeline of the parties alleged to have taken place:

May 15, 2020

A photo appears to show Johnson, his wife Carrie, then-Chief Adviser Dominic Cummings and Principal Private Secretary Martin Reynolds sitting around a table in the Downing Street garden sharing cheese and wine.

The picture, which emerged last month, also shows four other people gathered around a nearby table, drinking, and a separate, larger group standing a short distance away.

Johnson has dismissed speculation the image is documentation of an event held in breach of COVID-19 restrictions, insisting those seen gathered within it were “people at work talking about work”.

At the time, the UK was still under its first nationwide lockdown. Schools were shut to most pupils, pubs and restaurants were closed, and there were strict controls on social mixing.

Two people from different households were allowed to meet outdoors but only if they maintained a distance of two metres (6.5 feet). Guidance issued for workplaces said in-person meetings should only involve “absolutely necessary participants”.

May 20, 2020

About 40 people, including Johnson and his wife, reportedly attend a “bring your own booze” party in the Downing Street garden.

As revealed earlier this week, an invitation to the event had previously been sent out via email to some 100 members of the prime minister’s staff by Reynolds.

Johnson told the UK’s Parliament on Wednesday that he had been present at the gathering, which he claimed to have thought at the time was a work event.

The prime minister said he had entered the Downing Street garden to thank members of his staff for their work during the pandemic before returning to his office 25 minutes later.

He said that in hindsight, he should have stopped the event from continuing.

The same lockdown rules were in place at the time as those which applied five days earlier, on May 15.

November 13, 2020

Johnson reportedly gives a leaving speech to a departing member of his staff at an event attended by a small number of people and allegedly attends a party in his private Downing Street residence, in London.

Unnamed sources told the BBC that several staff members attended the gathering in his flat, along with Johnson’s wife. The broadcaster quoted a spokeswoman for the latter as denying the party took place.

November 25, 2020

About two dozen civil servants stage an impromptu drinks party in the Treasury, weeks after a second national coronavirus lockdown came into force, according to media reports citing unnamed government sources.

Chancellor Rishi Sunak, who had delivered his Autumn Budget and Spending Review earlier in the day, was reportedly not among the attendees and was allegedly unaware of the event prior to it taking place.

A spokesperson for the department later insisted it was a “small number” of staff who had attended the gathering.

At the time, people were banned from socialising indoors with members of another household. Pubs, restaurants and shops were closed and people were told to remain at home unless there was a specific reason to leave, such as for work or education.

November 27, 2020

Johnson allegedly delivers another farewell speech for an aide leaving Downing Street at a crowded leaving party.

UK newspaper The Guardian reported that the prime minister mentioned how busy the event was while delivering his remarks, citing an unnamed source.

The same lockdown rules were in place at the time as those which applied two days earlier, on November 25.

December 10, 2020

The Department for Education allegedly stages an office gathering in London to thank staff for their work during the pandemic.

About two dozen people reportedly attended the event, which was held in the department’s canteen, with drinks and snacks supplied.

A senior civil servant later said the party had been instigated by then-Education Secretary Gavin Williamson.

Though the second national coronavirus lockdown had been officially lifted by the time of the event, coming to an end on December 2, social mixing indoors between members of different households was still banned in London and many other parts of England as Johnson’s government pursued a regionalised approach to continued virus restrictions.

December 14, 2020

A high-profile Conservative Party figure stages a gathering at the party’s headquarters in Westminster, London.

The event was organised by campaign staff of the Conservatives’ then-London-mayoral candidate, Shaun Bailey, who was pictured at the party alongside more than 20 other people.

Bailey, who went on to lose in his bid to take over from incumbent London Mayor Sadiq Khan, later resigned from two London Assembly committees after news of the gathering emerged.

The event took place on the same day it was announced tougher restrictions on socialising would be imposed on London from December 17 as it moved from Tier 2 to Tier 3 under the government’s regionalised approach to virus measures. Social mixing indoors between members of different households was still banned.

December 15, 2020

Johnson reportedly takes part in an online Christmas quiz organised for his Downing Street staff, apparently violating social distancing rules as he does so.

A picture published by UK newspaper the Sunday Mirror last month appeared to show the prime minister taking part in the event while sitting in the Downing Street library, flanked by two members of his team. Johnson subsequently denied any wrongdoing.

Virus restrictions in place for London at the time meant social mixing indoors between members of different households was banned.

December 16, 2020

Staff at the Department for Transport stage a party in its offices in London, on the same day that the capital enters Tier 3 restrictions.

UK newspaper the Daily Mirror reported last month that nearly a dozen people were present at the event and that attendees were drinking and dancing.

Transport Minister Grant Shapps was not among those gathered, and later said he had “no idea” about the party until after it took place.

December 18, 2020

A Downing Street Christmas party takes place, reportedly featuring between 40 to 50 people.

Officials and political staff allegedly ate cheese, drank wine and swapped presents at the event, which went on late into the evening.

Johnson’s office initially denied the party had taken place, but a video obtained by UK broadcaster ITV News subsequently showed the prime minister’s then-press secretary Allegra Stratton joking about reports of a gathering.

“This fictional party was a business meeting and it was not socially distanced,” Stratton, who has since resigned, was recorded as saying.

The Christmas party took place when London was still under Tier 3 restrictions, meaning indoor gatherings of two or more people from different households were banned. Work parties were also prohibited at the time.