Serbia is being removed from a list of where people returning to or visiting England can avoid quarantine, on the day the new rules come into force.
The UK Government announced that the Joint Biosecurity Centre and Public Health England have “updated their coronavirus assessments of Serbia based on the latest data”.
Serbia was included on a list of 76 countries and territories from which people arriving into England will no longer need to self-isolate for 14 days from Friday.
The Welsh Government and the Northern Ireland Executive decided to follow the same approach, but the Scottish Government produced a list of just 39 countries not including Spain or Serbia.
There have been two nights of violent clashes in Serbian capital Belgrade by thousands of people protesting against coronavirus lockdown measures.
Serbian authorities have reported 352 coronavirus deaths and 17,342 cases, but it has been claimed the data does not represent the full impact of the virus.
UK holidaymakers were looking forward to meeting new grandchildren and being reunited with loved ones as they travelled on the first day of the new quarantine rules being in place.
Passengers passing through Gatwick Airport’s north terminal admitted they would not be travelling if they were still required to self-isolate for two weeks on their return.
“We probably would have gone later,” said Ray Gordge, 64, from Taunton, who was on his way to Paris to see his daughter for the first time in six months, and meet his new grandson, born last week.
“It’s exciting, I’m pleased the quarantine has been lifted to be honest,” he told the PA news agency.
“It’s nice to have a bit more normality.”
Mr Gordge said he only booked his easyJet flight in the last few days, but had no concerns about travelling.
“I think it’s OK as long as you’re wearing a face mask. It’s very strange.”
A “very excited” Mr Burgin said he was heading to Basel in Switzerland to see his girlfriend for the first time in about five months.
Commenting on the relaxation of travel quarantine rules, he admitted: “I wouldn’t be going if the changes hadn’t been made.”
Asked if he felt safe flying, Mr Burgin said: “It depends how busy the flight is going to be.
“I think it’s going to be difficult to maintain social distancing, but I also think the chances of coming into contact with someone with Covid is pretty low and they seem pretty on the ball with masks and things.”
Gatwick chief executive Stewart Wingate said the relaxation of the rules “makes a massive difference”.
He explained: “About 75% of the destinations we serve are now quarantine-free for passengers coming back into Gatwick.
“From a consumer point of view what we’re hoping is that will persuade people to take advantage of the flights.”
While Labour welcomed the UK Government’s relaxation of the quarantine for some countries, it criticised ministers for failing to secure agreements with more destinations to accept UK visitors without restrictions.
Shadow transport secretary Jim McMahon said: “The fact they have been unable to negotiate air bridges is an indictment of their failure to tackle the crisis at home.”