Professor Neil Ferguson - one of the U.K.'s most outspoken pro-lockdown scientists - is of the "do as I say not as I do" school of scolds.
Ferguson, whose group of scientists at London's Imperial College had convinced the ministers to impose stringent rules on social distancing, said that he acted in the belief that he was immune, having tested positive for coronavirus, and completely isolated himself for nearly two weeks after developing symptoms.
On Tuesday Ferguson released a statement to The Daily Telegraph saying he accepted he made "an error of judgement" and confirmed he was stepping down from his role in Sage, the Government's Scientific Advisory Group.
He had just finished a two-week period of isolation after testing positive for Covid-19 and said he had "acted in the belief that [he] was immune" as a result of having contracted the disease.
I regret deeply any undermining of the clear message on the continued necessity of social distance to control this devastating epidemic. "The federal government steerage is unequivocal, and is there to give protection to all folks".
Hancock said, "Professor Ferguson is a very eminent and impressive scientist and the science that he has done has been an important part of what we have listened to".
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Vallance told the Health and Social Care Committee that there was evidence people who have had coronavirus develop antibodies are likely to provide "some degree of protection from immunity".
Scotland Yard said Prof Ferguson's behaviour was "plainly disappointing", but ruled out issuing a fine.
Prof Ferguson's modelling of the virus's transmission suggested 250,000 people could die without drastic action. On March 18, he tweeted that he had a fever and cough, symptoms of COVID-19, and that there was a small risk he had infected others.
"I've been there since, I've been working from home and returned to Westminster last night to do this press conference because Parliament returns next week", he said in April.
The paper said merely slowing the spread of the virus, which had at that point been the aim, would have led to the NHS being overwhelmed by cases. Visiting someone in another household, including a partner who lives separately, is not allowed.
A statement from Imperial College London said Prof Ferguson "continues to focus on his important research".