A former UK civil servant has apologised for a "heartless and thoughtless" comment suggesting that "chickenpox-style parties" could be used to build herd immunity to Covid.

Lord Mark Sedwill, who held the post of Cabinet Secretary - the UK Government's top-ranking civil servant - at the time when the pandemic struck in early 2020 told the UK Covid inquiry that he had not intended to minimise the seriousness of the virus.

The comments were made during a private meeting, but subsequently leaked to media.

Lord Sedwill told the inquiry that he had made the suggestion when it because clear that the spread of the virus was "inevitable" and he was looking at a way of managing it.

He said: “At no point did I believe that coronavirus was only at the same seriousness of chickenpox. I knew it was a much more serious disease.

“What I was trying to examine was: was there a way of managing that [the virus], given its highly differential impact that ensured that it spread through those for whom the disease was likely to be unpleasant rather than dangerous and that we could quarantine and shield those for whom it would be dangerous.”

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He added: “I understand that it must have come across that, someone in my role, was both heartless and thoughtless about this and genuinely I am neither.

"But I do understand that distress that must have caused, and I apologise for that.

The inquiry has heard that the UK Government expected herd immunity to Covid to be achieved by autumn of 2020, and only realised the need for a suppression strategy - to prevent the NHS from becoming overwhelmed - in March of 2020.

The inquiry was shown minutes from a Cabinet Office meeting dated February 6 2020 which suggested that a worst-case scenario was "very unlikely".

Inquiry chair Lady Hallett questioned why there was not a Cabinet-level focus on the "bad", as opposed to the "reasonable worst case" scenario?

Lord Sedwill agreed that there was "too much focus, including in the briefings to Cabinet, on the reasonable worst case".

The Herald: Lord Sedwill conceded that not enough was done in early 2020 to consider the 'bad' scenarios as well as the worst-case scenarioLord Sedwill conceded that not enough was done in early 2020 to consider the 'bad' scenarios as well as the worst-case scenario (Image: UK Covid Inquiry)

He also conceded that by the end of February levels of alarm inside the Government, given official warnings about the imminent crisis, "should have been" higher.

He said: "It's hard looking back to recall quite how extraordinary were the measures we later took.

"They were unconscionable at the time. And, therefore, I think your point about this instinctive human reaction is true.

"I think it was also the case at the end of February the number of cases in the UK was - on the data available - still very small.

"One can understand how non-experts not familiar with exponential movement might have misunderstood the pace at which the disease was moving."

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He acknowledged that Boris Johnson might have shared that optimism bias.

"He is an optimistic person," he told the hearing.

Lord Sedwill also acknowledged that it was likely he described Mr Johnson's Government as "brutal and useless".

In a diary entry from August 2020, Sir Patrick Vallance wrote that Lord Sedwill had complained "this administration is brutal and useless".

The former Cabinet secretary said he could not remember making those remarks, but added: "I don't doubt Sir Patrick's memory. It must have been a moment of acute frustration with something."

Lord Sedwill also acknowledged that he believed Matt Hancock should have been replaced as health secretary.

In one WhatsApp exchange with the now-Cabinet Secretary, Simon Case, Lord Sedwill remarked that removing Mr Hancock from the post would "save lives and protect the NHS".

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He told the inquiry this was "gallows humour", adding: "I had raised my concerns with the prime minister. That was not intended for him to remove Mr Hancock but to take a grip on the issue."

Lord Sedwill confirmed that when he quit his role as Cabinet Secretary in June 2020, he made his views on Mr Hancock clear to the then-PM.

In a witness statement to the inquiry, Mr Johnson has stated that he "did not have any concerns regarding the performance of any Cabinet minister including Matt Hancock" and did not recall having received advice from Lord Sedwill that he should be removed.