On Sunday, excitement over the reopening of travel and hospitality was tempered by fears that a more infectious virus type first discovered in India is spreading quickly, delaying further plans to reopen.

Boris Johnson, the Prime Minister, urged Britons to "take this next step with a heavy dose of caution."

“We are keeping the spread of the variant first identified in India under close observation and taking swift action where infection rates are rising,” he said.

“In order to keep the virus at bay, I urge everyone to be cautious and responsible while enjoying new freedoms today.”

In the United Kingdom, cases of the variant have more than doubled in a week, defying a national downward trend in infections and deaths achieved through months of hard work and a rapid vaccination drive.