Watch: COVID-19 - Can you travel anywhere this Christmas?
The options for people hoping to travel this Christmas have narrowed significantly.
Politicians took action after a new, more transmissible variant of COVID-19 was discovered, particularly in London and the southeast of England, but also across every part of the UK except Northern Ireland.
So, based on your location, where can you travel to this Christmas?
England: Tier 4
The guidance for those living under England's highest level of restrictions is that you should not leave your Tier 4 area, except for what the government calls "legally permitted reasons".
These include travelling to work when you cannot work at home; travelling to school or college or for caring responsibilities; visiting someone in a support bubble or attending a medical appointment.
Those in Tiers 1-3 should not travel into a Tier 4 area except for similar reasons.
England: Tier 3
Downing Street urges those in Tier 3 to "avoid" travelling outside their area, including for overnight stays, other than "where necessary" for work, education, caring, moving home, visiting a support bubble or for medical reasons.
People are advised not to leave a Tier 3 area to stay in a second home.
They are also urged to "carefully consider whether they must travel abroad".
England: Tier 2
Those in this level are urged not to travel to areas with tougher restrictions, but are allowed to travel through a Tier 3 area as part of a longer journey.
An overnight stay in Tier 3 is not recommended.
People are also advised to stick to Tier 2 rules if they travel to a Tier 1 area.
Exceptions include work, education and medical treatment.
England: Tier 1
People are advised to continue travelling for "reasons such as work, education, medical attention or caring responsibilities" - but to stay local and avoid travelling out of their area if possible.
First Minister Nicola Sturgeon has said a strict travel ban between Scotland and the rest of the UK will be kept in place over Christmas to try to stop the new variant of coronavirus from taking root.
Ms Sturgeon said the ban would cover the whole of the festive period. Travel within Scotland will be allowed on Christmas Day.
Chief constable Iain Livingstone, of Police Scotland, said he had authorised the "doubling of our operational presence in the border areas of Scotland".
He added: "These highly-visible patrols will be proactively deployed on our road networks to continue our operational activity to ensure drivers and vehicles are in a fit condition to drive.
"The patrols will also deter anyone who might be considering breaching the coronavirus travel restrictions."
Level 4 restrictions are in place across Wales - in line with Tier 4 rules in England.
The Welsh government advises "essential travel only" for caring responsibilities or where someone cannot work from home.
It adds: "Going on holiday is not one of the permitted reasons to travel under alert level 4, whether that is in Wales, elsewhere in the UK or overseas."
Travelling into, or within Wales, to visit a second home, or a boat or caravan, is not permitted.
People can travel into Wales for work purposes or to return home.
Anyone holidaying in Wales is asked to leave during Level 4 restrictions.
The government in Northern Ireland is "asking" people to limit bubbling on Christmas Day, Sky's senior Ireland correspondent David Blevins said, but there is no change in restrictions yet and no clear guidance for those hoping to commute home from the rest of the UK.
There will be stricter restrictions from 26 December, when people are advised to "avoid all unnecessary travel".
On Sunday, France suspended all means of transport to and from the UK for 48 hours including all incoming accompanied freight by road, air, sea or rail.
The Eurotunnel will shut for the same period, and the ferry terminal at the Port of Dover is closed to all accompanied traffic leaving the UK.
Ireland's restrictions on flights and ferries will last for an initial 48 hours before being reviewed during a cabinet meeting on Tuesday.
Germany will halt all flights arriving from the UK as will Italy.
The Netherlands has banned flights for at least the rest of the year and will assess "with other European Union nations the possibilities to contain the import of the virus from the United Kingdom".
Belgium's prime minister issued a ban for at least 24 hours while the situation was assessed.
Bulgaria will suspend flights to and from the UK at midnight until 31 January.
Austria and the Czech Republic are also imposing new measures against UK flights, with Prague announcing that people arriving in the country having spent at least 24 hours in UK territory will now need to self-isolate.
More countries are expected to impose restrictions, although Spain has decided against banning flights from the UK, instead requiring arrivals to have tested negative for COVID-19 up to 72 hours before they touch down.