UK Prime Minister Boris Johnson has announced a new four-week coronavirus lockdown across England, a dramatic strategy shift following warnings hospitals would become overwhelmed under his current system of localised restrictions.
"Now is the time to take action because there's no alternative," he said in a televised address to the nation from Downing Street, adding "the virus is spreading even faster than the reasonable worst-case scenario of our scientific advisers".
People in England will be told to stay at home under the new restrictions which begin on Thursday - with the closure of hospitality and non-essential shops.
Pubs, bars and restaurants will close, though takeaways will be allowed, and all non-essential retail will be shut.
The restrictions will be similar to those introduced at the start of the pandemic in March, however this time schools and universities are expected to remain open.
People will still be able to exercise outdoors, and travel to work if they cannot work from home, though restrictions on international travel are likely to be introduced.
MPs will vote on the new measures before they are introduced at 00.01 on Thursday, and when they lapse, the current tier system will be reintroduced.
Mr Johnson is joined by Professor Chris Whitty and Patrick Vallance in Downing Street, following a meeting of his Cabinet earlier in the afternoon.
The introduction of national restrictions marks a dramatic shift in government policy, as the Prime Minister has until now resisted pressure to reintroduce nationwide restrictions.
It comes after new data showed the extent of cases across England. The Office for National Statistics estimated that 568,100 people in households were infected with coronavirus in the week ending 23 October.
Members of the government's Scientific Advisory Group for Emergencies (Sage) have backed the introduction of more stringent measures.
Professor Jeremy Farrar said the consequences of sticking with the current "insufficient" restrictions would be "much worse" than going for a second lockdown.
The director of the Wellcome Trust said: "The sooner we act, the sooner we can start to recover. It will be a very difficult few weeks now and no one can underestimate the toll that will take on people.
"But the consequences of sticking with the current insufficient restrictions would have been much worse."
Sage member Professor Calum Semple told BBC Radio 4's Today programme: "For the naysayers that don't believe in a second wave, there is a second wave.
"And, unlike the first wave, where we had a national lockdown which protected huge swathes of society, this outbreak is now running riot across all age groups."
Professor John Edmunds said the only way to have a "relatively safe" Christmas is to take "stringent" action now to bring the incidence of the virus "right down".
It comes after a senior government scientific adviser said it is "definitely too late to think that the two-week circuit-breaker on its own will sort this out".
"It would bring it down a bit but it wouldn't be enough to bring (the R value) right down. A two-week circuit-breaker would have an effect but now almost certainly it would need to go on for longer to have a significant effect."
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Meanwhile Scottish First Minister Nicola Sturgeon has told Scots not to travel to England unless it is for "essential purposes".
She said the prevalence of the virus is lower in Scotland than in other parts of the UK, after stricter measures were introduced north of the border in September.
That saw Scots barred from going into other people's homes, and the Scottish government also acted to close bars and restaurants across the central belt in early October.
A new five-level system of restrictions for tackling coronavirus will come into force in Scotland on Monday, which will see travel restrictions imposed on many Scots.
In Level 3 areas - the second highest tier in the new Scottish system and which affects the central belt including Glasgow and Edinburgh, as well as Ayrshire and Dundee - people are urged not to go outside of their own local authority area.
In a series of tweets urging Scots to stick to the new rules, Ms Sturgeon also said people are being asked not to travel to or from England.
4/ Most importantly, we urge everyone to comply with current restrictions, including on travel. People should not travel to or from level 3 areas in Scotland and for now, we are asking people not to travel to or from England at all, except for essential purposes.— Nicola Sturgeon (@NicolaSturgeon) October 31, 2020
France and Germany announced national lockdown restrictions earlier this week, while in Northern Ireland pubs and restaurants were closed for four weeks starting on 16 October with the exception of takeaways and deliveries. Schools were closed for two weeks.
Wales is currently under a "firebreak" lockdown with leisure, hospitality and tourism businesses closed, and in Scotland the majority of people will be under Level 3 of a new five-tier system from Monday.
More than a dozen regions in England will move into Tier 2 restrictions today, including Carlisle, after an announcement was made on Friday evening.