UK Prime Minister Boris Johnson has cancelled Christmas for millions of people across London and south-east England after scientists said a new coronavirus variant is spreading more rapidly.
Johnson announced from Sunday areas in the South East currently in Tier 3 will be moved into a new Tier 4 - effectively returning to the lockdown rules of November. It is estimated to affect about 20 million people.
Non-essential shops, gyms, cinemas, hairdressers and bowling alleys will close for two weeks, and people will be restricted to meeting one other person from another household in an outdoor public space.
The rest of England will also see the Christmas "bubble" policy - allowing up to three household to meet up over the holiday period - severely curtailed, applying on Christmas Day only.
Johnson told a Downing Street news conference that he was making the changes with a "very heavy heart".
He said: "I know how much emotion people invest in this time of year, and how important it is, for instance, for grandparents to see their grandchildren, for families to be together.
"So I know how disappointing this will be. But we have said throughout this pandemic that we must and we will be guided by the science.
"When the science changes, we must change our response."
Johnson was forced into action after new figures on Friday night showed a 60 per cent increase in the weekly average case rate in London.
Johnson said he "bitterly regretted" the changes to the Christmas arrangements.
The Prime Minister told a Downing Street news conference: "We, of course, bitterly regret the changes that are necessary but, alas, when the facts change you have to change your approach.
"The briefing that I had yesterday about this mutation of the virus, particularly about the speed of transmission, was not possible to ignore."
The Prime Minister said the Government was following scientific advice over changes to coronavirus restrictions.
"Because the science is clearly changing and has changed in the sense that our understanding of this new virus, its transmissibility, has been radically shifted just in the last 24 hours."
Johnson added: "We simply can't ignore that and that's why we're taking these extra steps today to protect the country."
He said the new restrictions were necessary because of the spread of a variant coronavirus which was transmitting faster than the original.
He told a Downing Street briefing: "It seems that this spread is now being driven by the new variant of the virus that we spoke about earlier this week.
"Our advisers on the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag) have spent the last few days analysing this new variant - there's no evidence that it causes more severe illness or higher mortality but it does appear to be passed on significantly more quickly.
"This is early data and is subject to review but it is the best that we have at the moment and we have to act on information as we have it because this is now spreading very fast."
The area affected includes all of London and much of the south and east of England, including Kent, most of Essex, most of Surrey, as well Buckinghamshire, Berkshire, Hertfordshire, parts of Bedfordshire, Gosport, Portsmouth and Peterborough.
Various lockdown measures will also be introduced in Wales and Scotland.
Scotland's first minister Nicola Sturgeon announced a "strict travel ban" between Scotland and the rest of the UK for the Christmas holidays. Bubbles will only be allowed on Christmas Day, and all of Scotland will go into level four restrictions from Boxing Day.
The move follows new restrictions in other parts of the world.
Italy will also go into a nationwide lockdown during the Christmas and new year period.
The country will be under "red-zone" lockdown between Christmas Eve and December 27, and between December 31 and January 3, and January 5-6, when Italy celebrates the feast of the epiphany.
And in Australia, residents of Sydney's northern beaches face restrictions as a new outbreak spreads quickly there. And there are fears a "restriction-free Christmas" is looking unlikely as residents are told to stay home until at least 11.59pm on December 23.
They can go to work, but bars, gyms and churches will be closed.
The only reasons residents will be allowed to leave home are to go to work or school, buy food, exercise, get medical care, to access childcare or provide care or for emergency assistance.
Confirmed cases of Covid-19 have visited a number of locations around Sydney including a gym, hair salon and several restaurants.
NSW Health has recorded another 23 cases of Covid-19 in the past 24 hours, with 21 of those linked to the new cluster. There are warnings to expect a repeat of those numbers today.
The area was essentially "going back to the restrictions that were in place back in March".
News.com.au reported that a restriction-free Christmas was looking virtually impossible for most of Sydney after health authorities, frantically contact tracing, added dozens of places to its alert list late last night.
And Western Australia is reinstating a hard border with NSW.
The Sydney to Hobart yacht race has been cancelled for the first time in 76 years.