He praised his fellow citizens for following the social distancing measures he recommended - meanwhile, UK scientist Neil Ferguson was secretly meeting his married lover.
He was forced to resign from his government advisory position yesterday after allowing Antonia Staats, 38, who lives with her husband and children in another house, to come to his home even as he lectured the public about the need to stop the spread of Covid-19.
Staats visited the professor at least twice - despite the fact he had just been in isolation for two weeks after testing positive for coronavirus.
Ferguson and his team at the Imperial College London used computer modelling to warn the government that more than 500,000 citizens would die unless the country went into lockdown.
Millions of other couples living apart across Britain have been unable to see each other for about seven weeks.
The 51-year-old had only just finished a two-week spell self-isolating after testing positive for coronavirus.
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Ferguson told the Telegraph: "I accept I made an error of judgment and took the wrong course of action. I have therefore stepped back from my involvement in Sage [the government's Scientific Advisory Group for Emergencies]."
He said he believed he was immune but that he deeply regretted undermining his own messages about social distancing.
Staat's first visit was on March 30, only a week into lockdown and the same day Ferguson told the nation they would have to remain in lockdown for another two months.
She visited again on April 8 - even though she had told friends she thought her husband, an academic in his 30s, had symptoms of coronavirus. The couple and their children live together in their South London home but are thought to have an open marriage.
She told her friends she believed her and Ferguson's households to be in the same bubble.
That's despite authorities telling the public that couples not living together had to stay apart during the lockdown.
Ferguson was a member of the Scientific Advisory Group for Emergencies (Sage), and the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), advising the UK's response to the pandemic. He gained the name "Professor Lockdown" for his work.
Transport Secretary Grant Shapps recently told the public they could only legally go outside for a medical emergency, daily exercise, essential food shopping and for certain types of work.
The police in England and Wales have handed out more than 9000 fines during the lockdown – equivalent to one every five minutes.
Scotland's chief medical officer, Dr Catherine Calderwood, resigned last month after twice travelling to her second home during lockdown.
• Covid19.govt.nz: The Government's official Covid-19 advisory website
Sir Iain Duncan Smith said: "Scientists like him have told us we should not be doing it, so surely in his case it is a case of we have been doing as he says and he has been doing as he wants to.
"He has peculiarly breached his own guidelines and for an intelligent man I find that very hard to believe. It risks undermining the Government's lockdown message."
Staats declined to comment.