BORIS Johnson has warned he may ban all Brits from leaving their homes within the next 24 hours unless they follow the social distancing rule and stay six feet apart.
The PM warned selfish Brits not listening to advice designed to save lives that he could soon enforce a more serious lockdown - similar to the ones in Italy, France and Spain.
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In his address yesterday, Mr Johnson said: "I don't think you need to use your imagination very much to see where we might have to go, and we will think about this very very actively in the next 24 hours.
"We need to think about the kind of measures we've seen elsewhere - other countries that have been forced to bring in restrictions on people's movements altogether, now as I say I don't want to do that."
There was anger at scenes over the weekend of crowds flocking to parks, markets, beaches and beauty spots.
It came as an 18-year-old was thought to have become the youngest victim of the virus in Britain as the number of deaths in the UK rose to 281.
Professor Kiran Patel, Chief Medical Officer for University Hospitals Coventry and Warwickshire NHS Trust said: "We can confirm that sadly a patient who was being treated for significant underlying health issues has passed away at University Hospital, Coventry.
"They had also tested for COVID-19 on the day before they died but this was not linked to their reason for dying.
"Our thoughts and condolences remain with the patient’s family and loved ones at this difficult time."
There are growing fears that Britain is on a similar trajectory to Italy - scene of the world's worst outbreak - where the death toll passed 5,000 over the weekend.
The Italian government was one of a number of European countries to announce new or extended restrictions - with Germany banning public gatherings of more than two people not from the same household.
Mr Johnson warned the NHS could be "overwhelmed" in the same way as the Italian healthcare system has been, if the spread of the virus in the UK is not curbed.
Speaking yesterday, Mr Johnson said: "Many, many people do not have access, let's face it, to private green spaces where they can do that and that's why parks, open spaces are so absolutely crucial for our country and for our society.
"But when we do that we have to do that responsibly...my message is you've got to do this in line with the advice, you've got to follow the social distancing rule - keep two metres apart.
"Otherwise if you don't do it responsibly...as you suggest there is going to be no doubt that we will have to bring forward further measures and we are certainly keeping that under constant review.
"Going outside now and taking exercise - you've got to take account of the medical advice and observe social distancing.
"If people can't do that, won't do that, don't do that then yes of course we're going to have to bring in tougher measures."
His warning came after Brits flocked to parks and beaches yesterday despite the warning to stay at home to beat deadly coronavirus.
Richmond Park was so full of cyclists, cars and walkers that police were called, as people failed to heed the urgent pleas to keep their distance.
In North London, Columbia Road Flower Market was packed with shoppers who were packed together, while dozens of people were seen standing in close proximity as they queued to buy chips in Barry Island, South Wales.
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Deputy chief medical officer Dr Jenny Harries said people who were congregating were "dangerous" and making outside environments "unavailable" to others.
Yesterday it was announced the National Trust would close all of its parks and gardens, with many other large parks around the country following suit - but many have remained open.
On Friday night, the PM ordered pubs and restaurants to close as part of efforts to encourage people to stay at home to fight the spread of Covid-19.
However many have remained open for takeaway service, leading to queues and groups of people sitting at cafes with outdoor tables.
Some MPs said there was now a clear mood for firmer action amid fears that further delay would cost lives.
Conservative former Cabinet minister Julian Smith said he would support "any measure" the government brought forward to force people to comply with the guidance.
Mr Smith, the former Northern Ireland secretary, said: "Many people have recklessly ignored government advice this weekend.
"I will support any measure the Government needs to force people to follow the guidelines designed to protect NHS staff and UK citizens' lives."
Meanwhile London Mayor Sadiq Khan said: "I am clear, life has changed and we have to do things differently for a while now.
"Social interaction will spread the virus. Do shopping for elderly neighbours, only buy what you need."
He added: "There are instructions and rules we need to obey to stop people dying.
"Making sure there is no confusion or mixed messages, people should not be leaving their homes unless they have to, they can walk dogs or exercise, but mixing socially leads to more people dying."
And six health experts yesterday warned Britain was losing a "very small window of opportunity" to help prevent the spread.
They said the government must stop people moving from region to region to stem the explosion of coronavirus cases in the UK.
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Yesterday letters to around 1.5million of Britain's most vulnerable were sent out by the government - telling them to stay at home to save their lives.
Housing Secretary Robert Jenrick confirmed thousands at risk of not recovering from coronavirus have officially been told to stay in for 12 weeks.
Earlier we told how doctors and NHS staff posted powerful pictures of their bruised faces after hours wearing protective gear to treat desperately ill coronavirus patients.
They shared the images after gruelling shifts as they battle against the killer bug.
The Sun Says
FOR the sake of this country — and to save the lives of others — we all need to take responsibility for our behaviour.
If we don’t then we face an Italy-style lockdown and will be forced to wave goodbye to our cherished freedoms.
It is often impossible for families to stay cooped up inside for days on end.
Parents of young children, especially, will find it tough. But there has to be some common sense.
We must all do our best to follow the Government’s advice to leave a 2-metre gap between ourselves and the next person when outdoors.
Yes, a bunch of irresponsible idiots think they’re invincible and are choosing to flout the rules. Flocking to beaches and parks to sunbathe in large groups is plainly not sensible.
Despite dire warnings that we are only a fortnight behind Italy where so many have died, large numbers of people here are still not getting the message.
Most Brits are keen to do what’s right.
But if not enough of us take heed then we face restrictions the like of which have never been seen before.
The stakes really are that high.