Dominic Cummings, Martin Reynolds and Lee Cain are among the former Downing Street employees who will be giving evidence to the COVID Inquiry next week.
It forms part of Module 2 of the UK COVID-19 Inquiry, which is "examining core UK decision-making and political governance".
Mr Cummings has previously provided bruising testimonies when appearing before public committees.
In May 2021, he appeared before a joint committee on technology and health, in which he criticised various aspects of the government's response to the pandemic.
And in a post on his blog earlier this month, Mr Cummings said he had been going through his statement to the inquiry in a "painful" process.
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Who is being interviewed?
This is the full list of people the inquiry is speaking to next week. It is mostly civil servants, alongside some political appointees and executives.
Proceedings will start at 10.30am on Monday, and then 10am on Tuesday, Wednesday and Thursday.
• Martin Reynolds, former principal private secretary to the prime minister; • Imran Shafi, former private secretary to the prime minister; • Lee Cain, former director of communications at Number 10; • Dominic Cummings, former adviser to the prime minister; • Stuart Glassborow, former deputy principal private secretary to the prime minister; • Helen MacNamara, former deputy cabinet secretary; • Dr David Halpern, president of the behavioural insights team; • Baron Stevens of Birmingham, former CEO of NHS England; • Sir Christopher Wormald, permanent secretary of the Department of Health and Social Care; • Professor Yvonne Doyle, former director for health protection at Public Health England.
Image:Martin Reynolds earned the moniker 'party Marty' Pic: UK Government
Image:Martin Reynolds earned the moniker 'party Marty' Pic: UK Government
Why is this interesting?
The early days of the pandemic were, by all accounts, a chaotic time in government. Downing Street was trying to get to grips with a global health crisis unprecedented in modern times.
Politicians involved will be interviewed at a later date, but what the next week will likely glean is how decisions were made by those behind the scenes.
The power structures within Downing Street are of particular interest, especially during the period when Boris Johnson was hospitalised.
There were criticisms levelled at both Mr Cummings and Mr Cain during their time in Downing Street that they wielded too much power, especially during this period.
Both men left Downing Street at the end of 2020. Since that time, Mr Cummings has been very critical of numerous ministers and other people in Downing Street at the time.
Speaking on the Political Currency podcast, former Tory chancellor George Osborne said he understood there were some "staggering" messages - not just sent "by Boris Johnson, but key advisers like Dominic Cummings".
He added that these might disclose "some things that are going to cause some real problems for individuals who are in charge at the time".
Read more: COVID Inquiry turns its focus to politicians Messages reveal govt 'infighting' at start of pandemic
Could this impact Rishi Sunak?
Last week, it was revealed that scientific advisers had referred to Rishi Sunak - who was then the chancellor - as "Dr Death" following the Eat Out to Help Out scheme.
And there is potential for more such damaging insights to come out from these evidence sessions.
Both Mr Cain and Mr Cummings made public statements last year during the first Conservative leadership race, when Mr Sunak claimed he was gagged over the negative effects of COVID lockdowns and that scientists had too much influence
Mr Cummings said the interview from Mr Sunak was "dangerous rubbish".
Mr Cain said that - while he was a "huge admirer" of Mr Sunak - the ex-chancellor's account was "simply wrong".
So it is not outside the realm of possibility that more uncomplimentary facts about the current prime minister come to light.
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COVID 'chaos' at No 10
What about partygate?
Some of the names mentioned will be familiar to those who followed the partygate scandal.
Mr Reynolds - also known as "party Marty - became notorious for sending an email to Downing Street staff in May 2020 inviting them to "bring your own booze" to the garden of the building. This event ended up seeing a number of people fined.
Ms MacNamara had served as the government's ethics chief. She was fined over partygate gatherings due to a leaving party held in June 2020.
Mr Cain and Mr Cummings avoided much of the partygate controversy. Mr Cummings criticised the way an alleged leaving party held when he departed Downing Street was investigated.
Read more: Who's in the firing line after partygate inquiry findings? Key findings of report that sealed Boris Johnson's fate
What roles did they play during COVID?
Mr Cummings was one of the most powerful people in Downing Street, having helped run the successful Brexit campaign and Mr Johnson's election success in 2019.
Mr Cain ran the press operations in Downing Street, and was previously a journalist at The Sun and the Daily Mirror, as well as working in communications.
Mr Reynolds, Mr Shafi, Mr Glassborow, Ms MacNamara and Sir Christopher were all senior civil servants during the pandemic, and would have helped with the running of the departments they were part of - including the office of the prime minister.
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Dr Halpern is part of the behavioural insights team, a part of government which looks at how people act and seeks to change this to "drive positive change and help people, communities and organisations thrive".
Lord Stevens was the CEO of the NHS in England, while Prof Doyle was part of PHE, part of government that oversaw the NHS which has since been replaced with a different structure.
