The four aides are among the most influential people in politics, as Deputy Political Editor Anushka Asthana reports
Four of Boris Johnson's top aides have resigned in just 24 hours.
Policy chief Munira Mirza, director of communications Jack Doyle, principal private secretary Martin Reynolds and chief of staff Dan Rosenfield all quit on Tuesday.
The resignations came on the same day that chancellor Rishi Sunak sought to distance himself from the prime minister's Jimmy Savile smear on Sir Keir Starmer, telling a Downing Street press conference: "I wouldn't have said it".
Political Editor Robert Peston said that the majority of the resignations were Mr Johnson attempting to distance himself from the partygate scandal, in which some of his top team were involved.
There was pressure on Mr Doyle and Mr Reynolds to go, after ITV News revealed their involvement in two Downing Street gatherings during lockdown, while Mr Rosenfield was one of those behind the denials of before more details became public.
Mr Reynolds invited around 100 staff to "make the most of the sunshine" and "BYOB" in the Downing Street garden in May 2020 when the nation was under strict lockdown rules. This party is currently under investigation, along with 11 others, by the Metropolitan Police.
ITV News also reported that Mr Doyle made a thank you speech and handed out awards at an alleged Downing Street Christmas party on December 18. Said party is currently being investigated by the police.
Mr Doyle is understood to have attended at least one other gathering.
However, it is though that the resignation of policy chief Ms Mirza will have rocked Mr Johnson as she has been at his side for 14 years.
Addressing MPs on Monday, in the wake of the publication of Sue Gray's report into allegations of Covid-19 lockdown-breaking parties in Downing Street in which she said there was a "failure of leadership in Number 10", Mr Johnson said there would be personnel changes at the top.
Political Editor Robert Peston analyses the four resignations
"In a nutshell, Johnson cleared out Reynolds, Doyle and Rosenfield to try to prove he is still in charge of events, after Mirza said he was scurrilous and quit," reports ITV News Political Editor Robert Peston.
"But it is a risky gambit, to put it mildly. He has just evicted the entire top layer of Downing St.
"If this were a private sector business, the shareholders would probably see that as definitive proof he lacks any management ability, and he would be toast.
"But Downing St is not a private company and only some Tory MPs behave like shareholders or even stakeholders."
Soon after the resignations, many Tory MPs began tweeting that they showed Mr Johnson was "taking swift and decisive change at No 10 to get us back on course and focused on people's priorities".
Despite No 10 attempting to show tough decisions are being made, the PM's actions in recent days have not gone down well with the faithful.
Ms Mirza handed in her resignation over the remarks Mr Johnson made about Jimmy Savile in the Commons, while Mr Sunak sought to distance himself from them when he took part in a televised press conference.
The former No 10 policy chief cited the PM's refusal to apologise for the false accusation that Sir Keir failed to lock up paedophile Savile while he was director of public prosecutions.
During a debate on the Sue Gray partygate report on Monday, Mr Johnson said Sir Keir spent his time as head of the CPS "prosecuting journalists and failing to prosecute Jimmy Savile".
Asked about the comments, Mr Sunak said: "Being honest, I wouldn't have said it and I'm glad the prime minister clarified what he meant."
Earlier in the day, the chancellor did not rule out a leadership bid if Tory MPs force out Mr Johnson over allegations of lockdown-breaching parties in Downing Street and during the televised press conference, social media users said the chancellor was positioning himself for a leadership bid if the PM resigns or is removed.
Mr Johnson backtracked on his claim on Thursday, accepting the Labour leader had "nothing to do personally" with a decision not to prosecute the disgraced entertainer.
But the clarification wasn't enough for Ms Mirza who suggested she was forced to resign over the lack of an apology.
In a letter to the prime minister, seen by the Spectator, she said: "I believe it was wrong for you to imply this week that Keir Starmer was personally responsible for allowing Jimmy Savile to escape justice.
"There was no fair or reasonable basis for that assertion. This was not the usual cut and thrust of politics; it was an inappropriate and partisan reference to a horrendous case of child sex abuse.
"You tried to clarify your position today but, despite my urging, you did not apologise for the misleading impression you gave."
The PM had also been urged to apologise by two of his own MPs, Julian Smith and Stephen Hammond.
Ms Mirza, who has spent 14 years working alongside Mr Johnson, added: "You are a better man than many of your detractors will ever understand which is why it is so desperately sad that you let yourself down by making a scurrilous accusation against the Leader of the Opposition."
Mr Johnson, in an interview with Channel 5 News, said he "of course" regrets making the comment after suffering the resignation.
In a statement Downing Street said it is "very sorry Munira has left No 10 and are grateful for her service and contribution to government".
She was swiftly replaced following her departure, with Conservative MP Andrew Griffith announced as head of the prime minister's policy unit.
The prime minister made the accusation on Monday while defending himself over the Sue Gray partygate report which condemned a "failure of leadership" in Number 10 under his watch.
On Thursday, the PM told broadcasters he wanted to "clarify" his remarks because "a lot of people have got very hot under the collar" about the widely debunked claim.
"Let's be absolutely clear, I'm talking not about the Leader of the Opposition's personal record when he was DPP (Director of Public Prosecutions) and I totally understand that he had nothing to do personally with those decisions," Mr Johnson said.
"I was making a point about his responsibility for the organisation as a whole. I really do want to clarify that because it is important."
Sir Keir told ITV's Good Morning Britain that accusation is a "slur, it’s untrue", a conclusion Full Fact came to when it investigated the claim in June 2020.
Savile died in 2011 aged 84 having never been brought to justice for his crimes. He is now believed to be one of Britain's most prolific sex offenders.
As the Savile row rumbles on, Mr Johnson is thought to be trying to distancing himself and attempting to show he is taking decisive action over the partygate scandal.
It is thought Mr Doyle, Mr Rosenfield and Mr Reynolds were all forced out.
According to the Daily Mail, Mr Doyle told staff as he resigned: “Recent weeks have taken a terrible toll on my family life. Thank you all for your hard work and dedication. I wish you all the best for the future.”
However, Mr Doyle reportedly added that he had always intended to resign after two years.
The PM is said to have previously refused Mr Doyle's resignation, but on Thursday a Downing Street spokesperson confirmed his departure, saying: "He has made a huge contribution and the prime minister is immensely grateful for the work he has done".
Downing Street also confirmed that chief of staff Dan Rosenfield had resigned. The Times had previously reported that Mr Rosenfield took part in the December 18 party.A No 10 spokesperson said on Tuesday: “Dan Rosenfield offered his resignation to the prime minister earlier today, which has been accepted.
"Martin Reynolds also informed the prime minister of his intention to stand down from his role as principal private secretary and the prime minister has agreed to this.
“He has thanked them both for their significant contribution to government and No 10, including work on the pandemic response and economic recovery."
Recruitment for both roles is underway, while officials have said Mr Reynolds will return to the Foreign Office.
Thursday's high-profile exits leave the prime minister further isolated as he battles to remain in charge, with 13 Conservative MPs having publicly called for his resignation over the way he has handled the partying claims.
More are believed to have done so privately but the number of letters to the chair of the 1922 Committee of backbench Tories has not yet hit the 54 required to trigger a no confidence vote.