The scientist whose advice prompted Boris Johnson to lock down Britain resigned from his Government advisory position on Tuesday night as The Telegraph can reveal he broke social distancing rules to meet his married lover.
Professor Neil Ferguson allowed the woman to visit him at home during the lockdown while lecturing the public on the need for strict social distancing in order to reduce the spread of coronavirus. The woman lives with her husband and their children in another house.
The epidemiologist leads the team at Imperial College London that produced the computer-modelled research that led to the national lockdown, which claimed that more than 500,000 Britons would die without the measures.
Prof Ferguson has frequently appeared in the media to support the lockdown and praised the "very intensive social distancing" measures.
The revelation of the "illegal" trysts will infuriate millions of couples living apart and banned by the Government from meeting up during the lockdown, which is now in its seventh week.
On at least two occasions, Antonia Staats, 38, travelled across London from her home in the south of the capital to spend time with the Government scientist, nicknamed Professor Lockdown.
The 51-year-old had only just finished a two-week spell self-isolating after testing positive for coronavirus.
Prof 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].
"I acted in the belief that I was immune, having tested positive for coronavirus, and completely isolated myself for almost two weeks after developing symptoms.
"I deeply regret any undermining of the clear messages around the continued need for social distancing to control this devastating epidemic. The Government guidance is unequivocal, and is there to protect all of us."
The first of Ms Staat's visits, on Monday March 30, coincided with a public warning by Prof Ferguson that the one-week-old lockdown measures would have to remain until June.
Ms Staats, a left-wing campaigner, made a second visit on April 8 despite telling friends she suspected that her husband, an academic in his 30s, had symptoms of coronavirus.
She and her husband live together with their two children in a £1.9 million home, but are understood to be in an open marriage. She has told friends about her relationship with Prof Ferguson, but does not believe their actions to be hypocritical because she considers the households to be one.
But one week before the first tryst, Dr Jenny Harries, the deputy chief medical officer, and Matt Hancock, the Health Secretary, clarified during the daily Downing Street press conference that couples not living together must stay apart during lockdown.
Prof Ferguson sat on Sage, whose advice has guided the Government response during the pandemic, as well as the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), which advises the chief medical officer and the Department of Health.
Grant Shapps, the Transport Secretary, recently reminded the public that it was "illegal to be outside the home for one of any other than four reasons". Those reasons are medical emergency, daily exercise, essential food shopping and certain types of work.
Police in England and Wales have handed out more than 9,000 fines during the lockdown – equivalent to one every five minutes, while Scotland's chief medical officer, Dr Catherine Calderwood, was forced to resign last month after making two trips to her second home during the coronavirus lockdown.
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."
Sir Charles Walker, a senior Conservative MP, said: "People will be desperately missing those that they love, and I totally understand if that separation becomes too much to bear at times."
Ms Staats declined to comment.