We're going to wrap up our live coverage for the day.

To find out how today's announcement will affect you, put your postcode into our lockdown look-up here.

For more details on England's new tier four, including what it means and who will be in it, read this.

Today's live page was brought to you by Sarah Collerton, Dulcie Lee, Owen Amos, Penny Spiller, Joshua Nevett, Jasmine Taylor-Coleman and Emily Young.

Thanks for joining us.

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We’re wrapping up our live coverage of the coronavirus pandemic shortly. Before we do, here’s a reminder of the headlines on this, the 283rd day since the pandemic was confirmed by the World Health Organization (WHO).

In the UK:

• UK Prime Minister Boris Johnson said a planned relaxation of coronavirus restrictions would be cancelled for large parts of south-east and eastern England and cut to just Christmas Day for the rest of England
• He said new tier four restrictions will apply in all areas across south-east and eastern England currently in tier three, including London, from midnight. Those in tier four cannot mix indoors with anyone not from their household
• Mr Johnson announced the changes for England at a Downing Street briefing after scientists said a new coronavirus variant is spreading more rapidly
• In Scotland, First Minister Nicola Sturgeon said coronavirus restrictions will only be relaxed on Christmas Day before tighter rules come into force from 26 December
• Festive plans were cancelled for all but Christmas Day in Wales, where a national lockdown will be imposed from midnight tonight
• At the moment there are no plans to change the rules in Northern Ireland.

Elsewhere in the world:

• The US government approved a Covid-19 vaccine developed by Moderna - the country's second so far - paving the way for millions of doses to be distributed
• Italy became the latest European country to announce tighter restrictions over the Christmas and New Year period in an effort to curb a rise in coronavirus cases
• The office of French President Emmanuel Macron said he was in a stable condition and his tests results were reassuring, a day after he announced he had tested positive for the coronavirus
• In Turkey, officials said nine people had been killed after an oxygen ventilator exploded at a hospital treating coronavirus patients in the country’s south
• Chile’s President Sebastián Piñera was fined $3,500 (£2,588) for breaching coronavirus rules by posing for a selfie with a passer-by without a mask.

Image source, Reuters

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We can bring you some business reaction to Boris Johnson's announcement of tier four restrictions in the south and east of England, including London.

"The consequences of this decision will be severe," Helen Dickinson, chief executive of the British Retail Consortium said.

She said the government’s "stop-start approach" to coronavirus restrictions has been "deeply unhelpful" for retailers ahead of the usually busy and lucrative Christmas period.

Adam Marshall of the British Chambers of Commerce echoed Dickinson, calling on the government to "address the economic consequences of its actions".

He said that retailers needed extra financial support to get through the winter and beyond.

Federation of Small Businesses vice-chair Martin McTague said tier four restrictions would be a "hammer blow" to non-essential retailers.

"From shops to hairdressers, this would normally the one of the busiest times of the year," he said.

"Many will have bought extra stock and increased staff hours, now their takings are to disappear literally overnight."

Michael Kill, chief executive of the Night Time Industries Association, said retailers had "lost all confidence" in the UK government's strategy for tackling coronavirus.

"The unrelenting closing and reopening of businesses is costing owners hundreds of thousands of pounds, and coupled with the erratic decision-making around restrictions, is rapidly destroying the ability of the sector to bounce back," he said.

Image source, PA Media

London Mayor Sadiq Khan says moving the capital under tier four restrictions is "a bitter blow for Londoners who were hoping to spend time with loved ones safely this Christmas".

"This continued chaos and confusion could all have been avoided had the government not made irresponsible promises to the public and raised expectations about the Christmas period," he says.

"London faces its toughest Christmas since the war and the whole city will need to pull together to see us through this terrible period."

Mr Khan said implementing restrictions was not enough, and the government needed to increase testing capacity, provide greater financial support and make face coverings mandatory in all busy outdoor public spaces.

As Sir Patrick Vallance, the UK's chief scientific adviser, explained in the press conference earlier, coronavirus infections and deaths have been rising rapidly since the start of December in the UK.

There was a dip in November, when England went into a four-week lockdown, and restrictions remained tight in Wales, Scotland and Northern Ireland.

But UK-wide infections have now gone back up to the levels seen in October, with more than 27,000 new Covid-19 cases confirmed on Saturday.

Another 534 deaths were also recorded in the UK on Saturday, up from 489 a day before.

Those increases bring the UK’s total number of infections to 2,004,219 and deaths to 67,075, the latest figures show.

That means the UK has the sixth-highest number of deaths and infections of any country in the world, according to tallies kept by Johns Hopkins University, external.

There have been big changes announced to the Christmas rules for England, Wales and Scotland.

• In the new tier four in London, South East, and eastern England, you cannot socialise with people outside your household or bubble, even on Christmas Day
• In the rest of England, which are in tiers one to three, the five-day "mixing window" has been reduced to one day - Christmas Day
• Christmas bubbles will also only be allowed for 25 December in Scotland and Wales

Read more details here

Tier four restrictions will come into force from midnight tonight and will apply in all tier three areas across the south and east of England.

In south-east England, the areas affected are:

• Greater London (all 32 boroughs and the City of London)
• Kent
• Buckinghamshire (including Milton Keynes)
• Berkshire
• Surrey (excluding Waverley)
• Gosport, Havant, Portsmouth
• Rother and Hastings

In the east of England, the areas affected are:

• Bedfordshire
• Hertfordshire
• Essex (excluding Colchester, Uttlesford and Tendring)
• Peterborough

Read more about tier four and what it means here.

You can also check what the rules are in your area here.

Ms Sturgeon answers a question about people having to cancel Christmas plans.

She says her "message to everybody is: I'm desperately sorry". She says it "breaks my heart", and acknowledges "there will be heartbroken people listening to this right now".

She says this is a "once in a century pandemic" that "we just have to get through".

She asks people to "hunker down" and repeats a line from Irish poet Seamus Heaney she used in the Scottish Parliament previously: "If we winter this one out, we can summer anywhere."

Jayne McCormack
BBC News NI political reporter

England, Scotland and Wales have all announced changes to their Christmas restrictions this afternoon, but at the moment there are no plans to change the rules in Northern Ireland.

However, the first and deputy first ministers as well as the health minister have been holding various meetings today to discuss their response to the new variant of the virus.

BBC Scotland's chief political correspondent Glenn Campbell asks Scotland's First Minister Nicola Sturgeon whether with hindsight she wishes she hadn't bothered to relax restrictions over Christmas.

"No," she says. "I've always agonised over this. From the moment we announced relaxations... I've advised against using them unless absolutely essential.

"In my view they were only ever there in recognition of the fact that some people would find it impossible to leave loved ones alone".

She adds that she wouldn't have changed track "if it wasn't for what I'd been told today about this new strain".

Ms Sturgeon says all of the Scottish mainland will move to level four restrictions from 26 December.

Level four is the highest of Scotland's five levels - it stops households mixing, shuts pubs and restaurants and closes non-essential retail.

Level four will last for at least three weeks. Schools will not resume until 11 January, with online only until 18 Janaury - apart from key workers' children and the most vulnerable.

Ms Sturgeon says the new rules "make me want to cry".

"I know how harsh it is," she says, adding "but this virus doesn't care about anything apart from spreading as far and wide as possible".

Her message, she says, is stay home and stay safe this Christmas.

The planned five-day relaxation of Covid restrictions over the festive period has been cut back to just Christmas Day for the whole of Scotland – with advice to avoid any social mixing.

Indoor mixing in a bubble in Scotland will be allowed to take place on Christmas Day only, Scottish First Minister Nicola Sturgeon says.

"We will allow Christmas Day to go ahead, but as we have said from the start, only use this flexibility if you really, truly need to," she says.

"Our advice is still not to meet indoors even on Christmas Day with other households if you can possibly avoid it."

A maximum of eight people from three households will be allowed to meet on Christmas Day, "but again our advice will be to minimise those numbers as much as possible", Ms Sturgeon says.

Cross-border travel will no longer be permitted, but travelling within Scotland will be allowed on Christmas Day only.

Ms Sturgeon says there will be a strict travel ban from Scotland to the rest of the UK throughout the Christmas period.

"People from Scotland should not visit other parts of the UK, and vice versa," she says.

International travel advice will be issued next week - but Ms Sturgeon strongly advises against it.

Ms Sturgeon says if we don't act "firmly and decisively" to stop the new variant taking hold in Scotland, "by January our NHS could potentially be overwhelmed".

Ms Sturgeon says there have been 17 cases of the new fast-spreading variant confirmed in Scotland - but, she says, that is likely to be an understatement.

It may be at low levels, but it does pose a real risk, she says, "if we do not act and act firmly".

She says Scotland must act "firmly and deceisvely now, or it will take hold".

Scotland's First Minister Nicola Sturgeon has taken to the podium for her press conference.

She says the new variant of the virus means "very firm preventative action is now necessary", adding that this is "probably the most serious and potentially most dangerous juncture" since the beginning of the pandemic.

Image source, PA Media

The prime minister held a Covid briefing at Downing Street a short time ago.

He was joined by England's chief medical officer, Prof Chris Whitty, and the UK's chief scientific adviser, Sir Patrick Vallance.

Here are the key announcements:

• London, the South East and parts of eastern England are moving into a new tier four level of restrictions
• From midnight, residents in tier four must stay at home, with limited exceptions. Non-essential retail, gyms and personal care centres must close. Hospitality venues are already closed under tier three rules
• Household mixing indoors is banned - people can meet one other person from another household in an outdoor space only
• Travel into and out of tier four is not allowed, unless essential
• The "support bubbles" for adults living alone will continue
• The planned relaxation of Covid rules for Christmas has been scrapped for tier four areas
• For the rest of England, the rules allowing three households to meet will be reduced to Christmas Day only
• The new rules follow evidence that a new variant of the virus is spreading fast in the areas moved into tier four
• The new variant is responsible for an increase in hospitalisations, but there is no evidence to suggest it causes a more severe disease than the old variant or will be resistant to vaccines
• Boris Johnson says he made the decision with a “heavy heart” but “when the virus changes its method of attack, we must change our method of defence”
• Prof Whitty says it is important people in tier four areas don’t travel so they don’t spread the variant to other parts of the UK
• Sir Patrick says that while this is a “horrible moment, it is controllable and there is light at the end of the tunnel with the vaccinations having started”
• You can read more here

Image source, Reuters

Labour leader Sir Keir Starmer says "millions of families will be heartbroken by having Christmas plans ripped up", after this evening's announcement by the prime minister.

Sir Keir says he was frustrated as he had raised the issue of Christmas with Boris Johnson at Prime Minister's Questions on Wednesday, where the prime minister told people to have "a merry little Christmas".

The Labour leader says "today's announcement will only lead to confusion when people need certainty" and called on the government to display "decisive leadership".

Scotland's First Minister Nicola Sturgeon is about to give a news conference.

There was earlier a call between leaders of all four UK nations, after which Ms Sturgeon held a meeting of the Scottish cabinet.

The first minister will be joined at the news conference by interim chief medical officer Gregor Smith and national clinical director Jason Leitch.

You can read the latest data on virus cases in Scotland here.