All UK travel corridors, which allow arrivals from some countries to avoid having to quarantine, have now closed.
Travellers arriving in the UK, whether by boat, train or plane, also have to show proof of a negative Covid-19 test to be allowed entry.
The test must be taken in the 72 hours before travelling and anyone arriving without one faces a fine of up to £500.
All passengers will still be required to quarantine for up to 10 days.
The isolation period can be cut short with a negative test after five days in England, but it does not apply in Scotland, Wales or Northern Ireland.
The government has said the travel corridor closure will be in force until at least 15 February.