Thousands of Britons were re-jigging their vacation plans on Sunday hours after London surprised them and anyone else hoping to travel from Spain to Britain with a mandatory two-week quarantine period.
Foreign Secretary Dominic Raab said the move was "absolutely necessary" after Spain recorded more than 900 new Covid-19 cases for two days in a row.
But the speed of the decision surprised many - including British Transportation Minister Grant Shapps and his family - who were already in Spain, a top holiday destination for Britons.
The new policy was announced on Saturday and stipulated that those who had not left Spain by midnight that day would be subject to the quarantine.
"We took the decision as swiftly as we could and we can't make apologies for doing so," Raab told Sky News, pointing out that Britain had an obligation to react quickly as news came in of growing numbers out of Spain.
"Spain is a safe country for tourism," Foreign Minister Arancha Gonzalez Laya said on Sunday, claiming that a recent rise in new cases was normal and insisting the infection clusters were localized and under control.
Gonzalez Laya added that the Madrid government was working to persuade Britain to exclude its Canary and Balearic islands from its new policy and have it only applied to the parts of the country hit worst by the novel coronavirus.
Spain's latest outbreaks are concentrated in the Catalonia and Aragon regions.
Britain has suffered under the virus more than any other country in Europe and was accused earlier this year of taking too cavalier an attitude to the threat of the pandemic.
But Spain has also suffered more than most other European countries, with over 274,000 confirmed infections and over 28,400 deaths. It is also seeing infection rates tick upwards after a months-long lockdown was relaxed on June 21.
British government data shows 299,426 confirmed infections and 45,752 deaths so far. The country recorded over 700 new daily infections for four consecutive days since Thursday.
Britain's decision could send shockwaves through the tourism industries in both countries.
It might also raise questions about Britain's air bridge agreements with 70 other countries and territories which had been deemed safe for visiting amid the pandemic and not subject to quarantine rules.
But if the quarantine rules can be applied within a matter of hours, it might also make Britons less inclined to travel.
Tui, a German tour operator, announced on Sunday already that it would stop transporting vacationers from Britain to the Spanish mainland, though service would continue to Spain's Canary and Balearic islands. Service from Spain back to Britain would also continue.