Anyone entering England by air, rail or sea will have to take a COVID-19 test 72 hours before their departure or face an immediate fine of £500 ($680), the British government has announced.

The new rule will apply to all international arrivals, including U.K. nationals, who will be required to present a negative COVID result before they will be allowed to travel. Currently, it is only a requirement for entry into England, with Scotland, Northern Ireland, and Wales implementing their own border controls.

Arrivals from countries not on the U.K. "corridor" list of countries with agreements in place will still have to quarantine for 10 days regardless of the result of their test. Countries not exempt under the travel corridor program have to self-isolate for 10 days but this can be shortened if someone has a private test five days after their departure and it comes back negative.

Critics say the move comes too little too late as other countries have been requiring pre-departure negative test results for months, but British Transport Secretary Grant Shapps said the measure is being introduced now due to concern about new variants of COVID reaching the U.K. following a rapid mutation of the virus first detected in South Africa.

"The reason for doing it now is that we've got a very big concern about the South African and other mutations of this virus, and what we don't want to do is be in a position where the vaccine is rendered less useful by having different variants," he told the BBC.

Experts previously told Newsweek why closing the borders entirely would make little difference to rising cases in the U.K. as the new rapidly spreading variants are already within the country. The U.K. imposed a ban on direct flights from South Africa and restrictions on flights to the country after its new COVID-19 variant was detected in two people in England - one in London and the other in the northwest.

Both were contacts of people who traveled to South Africa. It is already the dominant virus variant in the Eastern and Western Cape provinces of South Africa and has now spread to other countries including Austria, Norway, and Japan.

Health Secretary Matt Hancock was questioned over the border issue by his predecessor Jeremy Hunt, who has called for U.K. borders to shut in light of new COVID mutations. At a meeting of the U.K. government's health and social care committee, Hunt asked Hancock why Britain was not following east Asian countries in implementing border controls, like pre-departure tests. "We're not doing as much as South Korea and Singapore, even now," he said.

Hancock said the U.K. has full restrictions on people returning from South Africa, with only British nationals allowed to fly home before going into quarantine, and suggested similar measures will be taken if new variants are detected elsewhere in the world.

"We take a risk-based approach," he said. "After all if there's a country where the case rates are lower than the U.K., especially if there's no evidence of new variants, then there isn't a higher risk of someone coming here."

The test requirement will come into place next week, Shapps said. Prior to departure passengers will need to present proof of a negative COVID-19 test result to carriers, as well as a passenger locator form, identifying their U.K. address and contact details. Border Force officials will conduct spot checks on arrivals into England and anyone who has not provided proof of a negative test and locator form will be issued an on-the-spot fine. Children under 11 and lorry drivers are exempt.