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Unlike the first lockdown in March, which was open-ended, the new measures are expected to last for around a month until 2 December.
People must not mix inside homes, other than for childcare or other forms of support, while pubs and restaurants must close, along with non-essential shops. Takeaways can remain open.
Schools and universities, however, will be allowed to remain open.
Travel within the UK is discouraged, apart from for work, and outbound international travel will be banned - again, with work as an exception.
Johnson also announced that the furlough scheme would continue throughout November.
Government figures show that in the past day, a further 21,915 people have tested positive for coronavirus, bringing the UK total to 1,011,660.
Yesterday, news broke that the government was considering a national, month-long lockdown to curb the rising numbers of coronavirus cases.
The Prime Minister reportedly met with Rishi Sunak, Michael Gove and Matt Hancock to talk about the next steps after data showed that the country's hospitals are becoming overwhelmed - with fears that the UK could be on course for a much higher death toll than during the first wave unless further restrictions are brought in, according to the BBC.
In the strange, confusing limbo that followed the leak, many business owners have expressed their concern about the nature of the second lockdown.
Jonny Heyes, the owner of Common - a bar and pizza restaurant in Manchester's Northern Quarter - told LADbible he feels action has come too late for businesses like his to prepare sufficiently.
Heyes said: "I'd probably say that we've seen this coming. I kind of feel most of the general public had.
"It seems that once again the government are behind the curve and now we'll have to lock down more severely for longer, we don't know what support we're going to get, we don't know what we can and can't do.
"If the government had committed to a circuit breaker a month ago and given us time to plan then it would've been so much easier. Half term was a massive missed opportunity.
"It's clear that the only way to bring back demand is to reduce the level of virus, the only way to do that is stricter measures. Let's get this done and maybe plan in another circuit breaker in January, then in between we can do some business."
Tom McNeeney, who operates several hospitality businesses in Greater Manchester as part of the Lancashire Hospitality Co-operative, added: "There's a complete lack of competence here.
"This suddenly isn't sound bites and internal affairs anymore, their failings in leadership are going to cost thousands of businesses and countless jobs and, in the long term, almost certainly lives, as a direct result of their recklessness."
The announcement follows the introduction of similar measures in other European countries such as France, Germany and Belgium.
The second French lockdown came into effect this week, as the number of coronavirus-related deaths continues to rise in the country - with fears that hospitals are now buckling under the pressure.
Under the new restrictions, people are no longer allowed to leave their house unless it is for essential work or medical reasons.
Schools and shops will remain open, but non-essential businesses including bars and restaurants have been ordered to close.
President Macron said curfews in Paris and other major cities had failed to stem the tide of infections, saying in a televised statement: "Our target is simple: sharply reducing infections from 40,000 a day to 5,000 and slowing the pace of admissions to hospital and intensive care."
He added: "No matter what we do, nearly 9,000 people will be in intensive care by mid-November."
While Macron acknowledged that the new restrictions are 'heartbreaking', he said he 'could never stand by and see hundreds of thousands of our citizens die'.
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