The UK is now making it 3 or 4 covid tests before being released from quarantine for all (except the very few usual exceptions) arrivals in the UK.
A PCR (all of the tests are PCR) negative three days before travel, then
A PCR negative 2 days after arrival (either at the airport hotel or home depending on where travel originates), then
A PCR negative 8 days after arrival,
then released from quarantine 10 days after arrival if all are negative.
A fourth test, a PCR negative, on the 5th day after arrival can shorten the quarantine when come back negative, but the 8 day test is still needed.
All these tests have to be paid for by the traveller, even for British residents and citizens. The BBC said this morning that that will run in the region of £500 per passenger for the 4 tests.
Fines of up to £10,000.00 and jailing for up to 10 years for breaking those travel laws.