Anyone arriving into the UK from 33 "red list" countries will now be forced to quarantine in a hotel - or face ten years in prison.
The travel rules, which take effect today, mean people have to pay almost €2,000 each for a room.
In Scotland, the rules apply to all international arrivals.
British foreign secretary Dominic Raab says the UK government has booked beds in hotels to cater for demand.
"It's only one additional measure if you'd like, one additional safeguard in the lines of defence we've got against new variants coming in.
"But I do think it's significant and important, on top of the other border based restrictions we've now put in place."
