Deputy chief scientific adviser Professor Dame Angela McLean, addressing the same question, said she suspected “simple strategies might well turn out to be the best to use”.
Welsh First Minister Mark Drakeford earlier said the lockdown will not end in Wales next week, insisting “we will not throw away the gains” by “abandoning our efforts just as they begin to bear fruit”.
Debate about the lockdown took place as Downing Street offered more hopeful news about the Prime Minister.
Number 10 said Mr Johnson remains in intensive care but is making “steady progress”, with further updates expected on Thursday.
Mr Sunak said the PM was “sitting up in bed” and “engaging positively” with the medics treating him for Covid-19 at St Thomas’s Hospital in London on Wednesday.
But the boost came as the nation saw its record number of deaths in hospitals, with a rise of 938 taking the toll to at least 7,097, according to Department of Health figures.
Though significantly larger than the previous highest toll of 786, Prof McLean said new cases are not “accelerating out of control”.
At the daily Downing Street press conference, Mr Sunak unveiled a £750 million bailout to keep struggling charities afloat in the Treasury’s latest emergency measure.
Many charities welcomed the move but some also warned it must be the start – and not the end – of the Government’s efforts in protecting the sector.
Providing an update on Mr Johnson, a Downing Street spokeswoman said on Wednesday night: “The Prime Minister continues to make steady progress. He remains in intensive care.”
Number 10 earlier said the PM was no longer working while following the advice of doctors, and receiving just the “standard oxygen treatment” and “breathing without any other assistance”.
The PM’s three-week review into the lockdown measures had been due on Monday, but Downing Street is now saying it will be “on or around” that day.
Mr Sunak said the evidence to inform any review “will only be available next week”.
In Northern Ireland, Stormont minister Deirdre Hargey indicated there will be no relaxation of restrictions there at next week’s review.
Though the death toll rose, Prof McLean said there was “good news” in the daily number of new cases, which is a better indicator of whether distancing measures are working than fatalities.
“This count of new cases in the UK, day by day over the last few weeks, is not accelerating out of control,” she said.
NHS England’s national medical director Professor Stephen Powis warned that “this is not the time to become complacent”, however.
“We are beginning to see the benefits, I believe (of following Government measures), but the really critical thing, I believe, is that we have to continue following instructions, we have to continue following social distancing, because if we don’t, the virus will start to spread again,” he said.
Elsewhere, the Royal College of Nursing warned a lack of protective equipment is “fundamentally compromising” the care nurses can give to patients.
Premier League players joined forces to create an initiative which aims to raise funds for NHS charities during the coronavirus pandemic and distribute them “where they are needed most”.
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