People have been urged to stay at home this weekend, despite the warm weather, to prevent the spread of coronavirus, as a key Government adviser warned that the lockdown measures are merely a “placeholder”.

Prime Minister Boris Johnson and Health Secretary Matt Hancock said the public should stick with the social distancing rules and resist the temptation to enjoy the sunshine forecast for swathes of the UK on Saturday and Sunday.

But it came as Professor Graham Medley, a pandemic modeller advising the Government, warned that Britain had “painted itself into a corner” with no clear exit strategy from the Covid-19 crisis.

He told The Times: “This disease is so nasty that we had to suppress it completely. Then we’ve kind of painted ourselves into a corner, because then the question will be, what do we do now?

“We will have done three weeks of this lockdown, so there’s a big decision coming up on April 13. In broad terms are we going to continue to harm children to protect vulnerable people, or not?”

Prof Medley added: “If we carry on with lockdown it buys us more time, we can get more thought put into it, but it doesn’t resolve anything, it’s a placeholder.”

His comments came after England’s chief nursing officer, Ruth May, urged people to think of two nurses who died after contracting coronavirus and “stay home for them”.

Areema Nasreen and Aimee O’Rourke, both mothers of three children, died alongside two healthcare assistants, it was announced on Friday.

Ms May, speaking at the daily Downing Street press conference, said: “This weekend is going to be very warm and it will be very tempting to go out and enjoy those summer rays.

“But please, I ask you to remember Aimee and Areema. Please stay at home for them.”

She added: “I worry that there’s going to be more and I want to honour them today and recognise their service.”

Meanwhile:

– The Department of Health confirmed 684 more people died in hospital after testing positive for coronavirus, bringing the total deaths in the UK to 3,605 as of 5pm on Thursday.

– Boris Johnson, who remains in self-isolation inside Downing Street as his coronavirus symptoms persist, said he is “feeling better”.

– The Queen will make an address to the nation about the coronavirus crisis on Sunday.

– The first of the Government’s emergency field hospitals to treat coronavirus patients opened in east London’s ExCel centre.

Mr Johnson urged people not to break social distancing rules as the weather warms up, even if they were going “a bit stir crazy”.

In a video on social media, he said: “I reckon a lot of people will be starting to think that this is all going on for quite a long time and would rather be getting out there, particularly if you’ve got kids in the household, everybody may be getting a bit stir crazy, and there may be just a temptation to get out there, hang out and start to break the regulations.

“I just urge you not to do that. Please, please stick with the guidance now.”