Boris Johnson has outlined strict new measures to tackle the spread of coronavirus, including a ban on public gatherings of more than two people.
In a televised statement on Monday, the prime minister ordered people only to leave their homes under a list of “very limited purposes”.
He also ordered the immediate closure of shops selling non-essential goods.
But police chiefs warned of phone lines being inundated with calls about what movements are still permitted.
Speaking from Downing Street on Monday evening, Mr Johnson said the country faced a “moment of national emergency” and staying at home was necessary to protect the NHS, save lives and tackle “the biggest threat this country has faced for decades”.
He said people may only leave home to exercise once a day, to travel to and from work where “absolutely necessary”, to shop for essential items, and to fulfil any medical or care needs.
The restrictions would be in place for at least three weeks and would be kept under constant review, the prime minister said.
“To put it simply, if too many people become seriously unwell at one time, the NHS will be unable to handle it – meaning more people are likely to die, not just from coronavirus but from other illnesses as well,” he said.
The prime minister’s spokesman said many ministers would dial into Tuesday’s cabinet meeting remotely, to comply with social distancing measures.