The travel industry reacted with fury after the latest measures were announced, despite ministers insisting they were only temporary.

Dominic Raab, the Deputy Prime Minister, told the Sky News Trevor Phillips On Sunday programme: “I know that is a burden for the travel industry but we have made huge, huge strides in this country. 

“We have got to take the measures targeted forensically to stop the new variant seeding in this country to create a bigger problem. We have taken a balanced approach but we are always alert to extra risk that takes us back not forward.”

Prof Woolhouse said that although the numbers of people with the omicron variant are “still quite small”, and likely to remain in the hundreds, they are “growing quite fast”. However, he added that vaccines would be “very, very good” at protecting against the variant.

Statistician Prof Sir David Spiegelhalter told Trevor Phillips On Sunday: “It’s a very difficult situation because we haven’t got a lot of data yet at all, almost nothing from this country about what the risks are.

“In South Africa, there’s data coming out showing pretty strong evidence that the increased risk of transmission and some evidence about people going to hospital, but it may actually be milder. But we haven’t got enough data yet to be able to say. It doesn’t look as if it’s really severe if you get it, I think that’s about all we can say at the moment.”

Asked whether measures to combat the spread of omicron have gone far enough, Prof Sir David added: “It’s best to be precautionary, when there’s so much we don’t know… and when we don’t know it’s better to be safe than sorry.”