A “highly concerning” new variant of the Covid-19 virus which is believed to spread easier than the mutant strain that resulted in the creation of the new Tier 4 restrictions has been discovered in the UK, Matt Hancock has said.

The variant, believed to be behind an increase in cases in South Africa, has been discovered in two people in the UK thought to be contacts of those who travelled between the two countries in the last few weeks.

The Health Secretary told a Downing Street press briefing that the discovery would result in urgent new quarantine rules for recent visitors from South Africa.

Mr Hancock said: “This new variant is highly concerning because it is yet more transmissible and it appears to have mutated further than the new variant discovered in the UK.”

He announced a range of new measures intended to reduce the strain spreading further, including placing the two people known to be infected with the South African strain into quarantine.

He added: “Anyone in the UK who has been in South Africa in the past fortnight and anyone who is a close contact of someone who has been in South Africa in the last fortnight, must quarantine immediately.

“They must restrict all contact with any other person whatsoever.”

He said the measures would be “temporary” while the new strain is investigated at Porton Down laboratories.

The “UK” strand of the coronavirus is believed to have mutated randomly in Kent as early as September, and prompted the Prime Minister to abandon the proposed relaxation of restrictions over Christmas.

Latest figures suggest the South African strain was behind a record number of people being hospitalised there.