International travel for xo non-essential reasons like going on holiday has been legal since 17 May, but with so few countries on the green list, the destinations where travellers can go without quarantining are few in number.
While the government has always said that international travel would be limited, the travel industry had not foreseen that the list would be as limited as it is, particularly now that Portugal has been moved to the amber list.
So what could get travel going again and what are the roadblocks?
While the government is concerned about importing new cases into the UK, the biggest concern is that tourists could bring in a vaccine-resistant variant that would render vaccination efforts useless and endanger public health.
The difficulty is working out when a variant - or in Portugal's case - a mutation, is significant enough to change a country's traffic light status.
Is it when it is classified as being "of concern", "of interest" or just when it's identified in the first place?
"The move from variant of interest, to variant of concern, has never been properly identified as the parameters to look at," Dr Bharat Pankhania, senior clinical lecturer at University of Exeter's Medical School tells the BBC.
"They mostly all start off as variants of interest and become variants of concern when displaying activities and properties of being more infectious, severe disease causing and bypassing the current vaccines."
Will islands reopen?
The industry had hoped that while mainland Greece and Spain might not yet be on the green list, at least some of the Spanish and Greek islands would be.
The island policy was used last year and Transport secretary Grant Shapps said in April that it was something his department wanted to consider.
But there are difficulties with looking at individual islands, partly because of their size.
"Healthcare facilities are limited and they can provide what they can and no more," says Dr Pankhania.
"There could come a time when a British holidaymaker is told, wait - we have Spanish people here who are sick and they could take priority, leaving holidaymakers stuck."