Holidaymakers from across the South East face being stuck in quarantine for 14 days after the government re-imposed quarantine rules for travellers returning from Spain over fears of a second wave of coronavirus infections in the country.
The decision to reimpose a quarantine was made after Spain recorded more than 900 fresh daily cases of the deadly respiratory disease for two days running.
The quarantine measures apply to mainland Spain, the Canary Islands and the Balearic Islands.
The Foreign Office is now advising against all but essential travel to mainland Spain.
Passengers travelling back to Gatwick Airport on Monday morning were shocked at the news they must quarantine after the "last minute" change of rules.
It's just really impacted on me as I've got 14 days to stay indoors.
Matt Wesson from Fareham in Hampshire had booked to fly to Tenerife on Tuesday.
He says his wife and four children are "disappointed" but he understands holidays abroad do come with a certain amount of "risk" at the moment.
We always knew there was going to be a risk with stuff like this happening at the moment, but when we booked it, it was sold as a quarantine free holiday.
Spain’s foreign minister said the Spanish government was working to have the tourist hotspots of the Balearic and Canary Islands exempted from the UK’s new quarantine measures.
Arancha Gonzalez Laya told reporters: “[This is] for two reasons – number one, these are islands, very safe territories; number two, their epidemiological data is extremely positive and well below epidemiological data in the UK.
Ms Gonzalez Laya refused to comment on whether the country will now start imposing quarantine rules on people coming from the UK, saying "this is not a political exercise".
A traveller who arrived at Heathrow Airport on Sunday morning told of her frustration over a delayed flight which meant both she and her husband must now quarantine at home for two weeks.
She told ITV News she could not understand why advance warning had not been given to travellers ahead of Saturday's decision, since coronavirus cases had been rising in Spain in the last few days.
This, she said "would give a lot more people the opportunity to not be so massively inconvenienced.
"Trust people to be a little bit more smart and give them the discretion to make their own decisions."
She added while her husband could work from home for the next two weeks, she had lost her job at the start of the lockdown and "going outside once a day is really, really important for my mental health".
However, she said her and her husband were "lucky... a lot of people are suffering much more serious consequences for this [quarantine] decision".