New temporary requirements for entrance into the U.K. came into effect on Nov. 30 to help prevent the spread of omicron, the new Covid-19 variant.
All international arrivals must take a PCR test by the end of their second day in the U.K. and self-isolate until they receive a negative test result.
Anyone who has come into contact with a suspected omicron case must self-isolate and will be contacted by the NHS Test and Trace, a body that tracks Covid-19 with the intent to prevent its spread.
Face coverings are mandatory on public transportation and in shops.
The new measures will be reviewed in three weeks.
In a statement, British prime minister Boris Johnson said, "The measures taking effect today are proportionate and responsible, and will buy us time in the face of this new variant."
Correction: All international arrivals must take a PCR test by the end of their second day in the U.K.