At Prime Minister’s Questions on Wednesday, Boris Johnson apologised after footage emerged of senior Number 10 staff joking and laughing about a Downing Street Christmas party last year - but told MPs he has been repeatedly “reassured” no such event occurred.
But who is Mr Case and what exactly will he be looking in to?
Who is Mr Case?
In September last year, Mr Case was appointed as the youngest-ever cabinet secretary and head of the civil service – a role that involves advising the prime minister of the day, leading the implementation of the government’s policies and managing other senior civil servants.
Mr Case joined the civil service in 2006 as a policy adviser for the Ministry of Defence, and for the next eight years, held roles in the Cabinet Office, Northern Ireland Office, Government Communications Headquarters (GCHQ) and the Olympic Secretariat – which oversaw the 2012 London Olympic Games.
In 2012, he became private secretary to then-prime minister David Cameron.
He later returned to Number 10, acting as part of the team involved in the early Brexit negotiations – but took a hiatus to become Prince William’s private secretary.
In 2020, Mr Case returned to Downing Street once more to help with the government’s response to the COVID-19 pandemic.
How will his investigation into Downing Street Christmas events work?
The PM announced in the Commons that Mr Case would carry out an independent investigation into any events that occurred in Number 10 on 18 December – when, according to sources who have spoken to Sky News, a party took place in Downing Street with around 40 people in attendance.
The PM’s official spokesperson later told reporters that the investigation would indeed only focus on potential events on 18 December, noting “this will be an independent process looking at allegations made on that day in Number 10”.
But while responding to an urgent question in the Commons on Thursday morning, Solicitor General Michael Ellis confirmed the cabinet secretary will look into alleged gatherings that occurred on 27 November and 10 December alongside the 18 December event.
Mr Ellis told MPs: “I can confirm to the House that the cabinet secretary’s investigation will establish the facts surrounding the following: allegations made of a gathering at 10 Downing Street on 27 November 2020, a gathering at the Department for Education on 10 December 2020, and allegations made of a gathering at 10 Downing Street on 18 December 2020.
“The primary purpose of the cabinet secretary’s investigation will be to establish swiftly a general understanding of the nature of the gatherings, including attendance, the setting and the purpose, and with reference to adherence to the guidance in place at the time.
“If required, the investigation will establish whether individual disciplinary action is warranted.”
Mr Ellis said officials investigating the matter will have access to “all relevant records” and be able to “speak to staff”.
What Christmas events in Downing Street allegedly took place?
• 13 November 2020
The PM’s then-chief aide Dominic Cummings left Number 10 clutching a box of his belongings, halfway through the second national lockdown.
According to Mr Cummings, despite the national lockdown, a party then took place in the Downing Street flat where the prime minister lives with his wife. Number 10 denies this.
The Times has also reported that separately that evening, the PM gave a leaving speech for his outgoing communications chief Lee Cain.
• 27 November 2020
During the second national lockdown, Mr Johnson gave a speech at a leaving party for a member of staff in Downing Street during the second national lockdown, according to reports in the Daily Mirror.
Tweeting on Thursday, Mr Cummings denied this was a party.
“There was no party on Fri 27/11. Red herring. A staff member left their job. Walked to press office to say bye, PM bumbled in & started babbling, everyone embarrassed, dispersed. Focus should be actual party in PM’s flat Fri 13/11 reported AT THE TIME but ignored by lobby!”, he posted.
• 10 December 2020
Permanent Secretary at the Department for Education Susan Acland-Hood has confirmed to MPs that a party was held at the department which was also attended by then-education secretary Gavin Williamson.
The event, first reported by the Mirror, was at a time when London was in Tier 2, with indoor mixing banned.
• 14 December 2020
The Times is reporting that a party was held at Conservative Campaign Headquarters (CCHQ) with Tory mayoral candidate Shaun Bailey and “at least two dozen party aides and volunteers”.
It is described by the newspaper as a “raucous bash”.
A Conservative spokesperson told Sky News: “CCHQ staff became aware of an unauthorised social gathering in basement of Matthew Parker Street organised by the Bailey campaign on 14th December. Formal disciplinary action was taken against 4 CCHQ staff seconded to the campaign.”
• 18 December 2020
Two days after Tier 3 restrictions come into effect in London – meaning people were not allowed to mix indoors with anyone outside their household or support bubble – a Downing Street wine and cheese night is said to have been held.
This event is what culminated in the resignation of Number 10 adviser Allegra Stratton on Tuesday following leaked video footage of her and other officials laughing about it four days later.
The Times reports this party went on until 2am and that Secret Santa gifts were exchanged.
Around 40 people were in attendance, according to sources who have spoken to Sky News.
The PM committed at PMQs to passing on everything the government knows about all parties to the Metropolitan Police.
The Met announced on Wednesday that they would not be investigating this event, despite the leaked video footage of Number 10 aides joking about the event, due to an “absence of evidence”.
What other investigations has Mr Case been involved with?
• Downing Street flat refurbishment
Boris Johnson and his then-fiancée Carrie were said to have carried out a lavish overhaul of the flat above 11 Downing Street in order to replace Theresa May’s “John Lewis furniture nightmare”.
Mr Case faced criticism over his personal involvement in sorting out the financial arrangements of the rebuilding of Downing Street.
In April, Mr Case confirmed he was looking into whether a trust could be established to help fund upgrades of the prime minister’s residence in Downing Street.
It was later disclosed that over £52,000 was given to the party by Lord Brownlow for the work, initially paid for by the Cabinet Office, after a row erupted earlier this year over how the refurbishment was funded.
On Thursday, the Conservative Party were fined £17,800 by the electoral commission for “failing to accurately report” this donation to the flat makeover.
Speaking before the ruling, one member of the government familiar with Mr Case’s involvement in the issue told Sky News: “I’m astonished that Simon has got involved in this himself.
“It has so much potential to go wrong. What is he involving himself in something like this for? It’s so odd.”
Labour also questioned why Mr Case was involved in such an apparently trivial matter.
• Downing Street ‘chatty rat’ scandal
In April, Mr Case left MPs frustrated about the progress of an investigation into government leaking which had been ongoing since the end of October 2020.
The so-called ‘chatty rat’ inquiry was founded after details of England’s second COVID lockdown emerged in the media before a formal announcement by the government.
Despite the probe lasting more than five months, Mr Case admitted in April that the culprit may never be found.
Appearing before the Commons Public Administration and Constitutional Affairs Committee, he also had to deny that the inquiry had been de-prioritised.
“In the time that has now passed, I think it is probable that the team will not successfully identify the source or sources but work is ongoing,” Mr Case said.
Former shadow chancellor John McDonnell accused Mr Case of delivering a “badly scripted version” of 1980s TV sitcom Yes Minister.