All international passengers will soon have to test negative for Covid-19 before travelling to the UK.
People arriving by plane, train or boat, including UK nationals, will have to take a test up to 72 hours before leaving the country they are in, reports the BBC.
Transport Secretary Grant Shapps said travellers "can't board... without having that negative test".
Even with a negative test, arrivals from countries not on the travel corridor list must still quarantine.
Shapps said the government was "very keen" to set up compulsory testing now because of the new variant of the virus circulating in South Africa, which he said was "causing great concern with the scientists".
"They're not sure whether for example the vaccine will be able to deal with it in the first place, and we're very, very keen to keep it out," he told BBC Breakfast.
The new South African variant has got some potentially concerning changes that experts are closely monitoring. While it is extremely unlikely the mutations would render vaccines useless, scientists are doing tests to make sure immunisation will still work well.
Even in the worst case scenario, vaccines can be redesigned and tweaked in a matter of weeks or months to be a better match if necessary, experts say.