The UK’s testing system could be overwhelmed if holiday hotspots are added to the green travel list, according to an industry expert.

Rory Boland, travel editor of Which?, has told Sky News “too many people are not getting their test back on time”.

The warning comes ahead of an expected review of the government’s travel traffic light system later today.

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Portugal is the only viable major tourist destination currently in the low-risk tier, but it’s thought Malta, parts of the Caribbean and the Greek islands of Zante, Rhodes and Kos could be added.

Holidaymakers returning to the UK from green locations are not required to self-isolate but they must take one post-arrival coronavirus test.

Mr Boland said the testing system is struggling to meet demand as it is.

“Providers to us were saying that it’s simply not set up to deal with the numbers of people who need to use it,” he told Sky News.

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“So if we see the Canary Islands, Spain, Greece – some big destinations that hundreds of thousands of people want to go to – turn up on the green list, it’s hard to see how that system is going to cope.

“It is at risk of being overwhelmed.”

Boris Johnson gave nothing away when asked about the review yesterday, even hinting at a possible expansion of the amber and red lists.

The prime minister warned: “I want you to know we will have no hesitation in moving countries from the green list to the amber list to the red list, if we have to do so.”

But many holidaymakers are optimistic, if on edge, ahead of the announcement.

“I’ve been on tenterhooks really the last couple of weeks,” Justine Hume, who is hoping to fly to Cyprus to get married later this month, told Sky News.

The island is currently an amber list location, meaning Ms Hume would have to quarantine at home for 10 days on return and take two post-arrival tests.

“We were supposed to have about 70 guests come over but you know not many are willing to do the amber 10-day isolation upon return,” she said.

“So we’ve got a lot riding on this – whether we have 70 guests, or seven!”

The Government has urged people against non-essential travel to amber countries. But having originally planned her wedding in the coastal resort of Paphos for 2020, and subsequently having to postpone it, Ms Hume is reluctant to change the date again.

“Because of the year we’ve had, we’re willing to do anything to get out there,” she said.