People are being urged to "think carefully" before making plans to meet up with family and friends over Christmas. Three households of any size will be able to get together for five days over the festive period in homes, places of worship and outdoors. Travel restrictions will be lifted to allow people to move freely across the UK. But the prime minister warned the public "not to throw caution to the wind" and encouraged extra care where relatives are vulnerable. Wales' First Minister Mark Drakeford summed up the warnings by telling people the relaxation was "not an instruction to meet".
Read the rules around Christmas bubbles in detail and our guide to the sort of questions to consider if you're deciding whether to get to together.
Some scientists have warned the relaxation could spark another wave of infections and further deaths, but ministers hope with compliance up to and after the five-day window the impact can be minimised. To that end, it's likely that relatively few areas of England will be placed in the lowest tier of restrictions after lockdown ends next week. We'll know for sure on Thursday.
BBC health correspondent Nick Triggle says ministers hope Christmas will provide the public with some much-needed respite. They also feel they have little choice to introduce a period of grace, he added, believing large numbers of people would simply choose to mix anyway.

Chancellor Rishi Sunak will explain later how he hopes to protect jobs and help the economy recover from the devastating impact of coronavirus. His Spending Review will announce money for the coming year for the NHS, schools and other public services, but there'll also be forecasts about how long the impact of the pandemic will be felt.
Some plans have already been announced - an increase in defence spending and a £4.6bn package to help the unemployed back to work, for example. We also expect a cut in the UK's overseas aid budget, and there have been reports of a pay freeze for the majority of public sector workers. What else might he do? Well, more money to tackle climate change and regional inequalities - that idea of "levelling up" - seem like decent bets. He might hint at future tax rises too.
The BBC will follow Mr Sunak's speech live and help make sense of it afterwards. In the meantime, read more about why what he'll say matters to us all, and four things to look out for in particular.

A shortage of personal protective equipment at the start of the pandemic led to the government paying £10bn more to secure sufficient supplies than if they'd bought it a year earlier. Spending watchdog the National Audit Office said not enough PPE had been stockpiled and unprecedented demand led to very high prices. Hundreds of millions were also wasted on "unsuitable" items that couldn't be used - for example, that fell below legal safety standards.
In its official response, the government said the report acknowledged NHS providers had been able to get what they needed - although the NAO heard feedback from staff who believed they were "not adequately protected during the height of the first wave".

The headline writers enjoy the news about festive household get-togethers. "The twelve rules of Christmas" is the Daily Mail's take, while the Daily Mirror goes for "Season's meetings". The Sun has had fun merging Boris Johnson's face onto the body of Slade frontman Noddy Holder, alongside the words "Here it is... mini Christmas". The Daily Telegraph also splashes on the rules for family "bubble" celebrations, but reports the PM had to "slim down" his original hopes for a week-long window following opposition from leaders in Scotland and Wales. The Daily Express takes to heart Mr Johnson's warning not to get carried away, telling readers: "Have a merry (but not so many) Christmas". Elsewhere, the Guardian has seen a confidential government document which admits the UK faces an increased likelihood of a "systemic economic crisis" as it completes its exit from the EU during the pandemic and potentially deals with other crises like winter flooding. The Cabinet Office tells the the paper it isn't a prediction, but the government has to be ready for all eventualities.

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