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A huge door-to-door testing mission is getting under way in a bid to find "every single case" of a new coronavirus variant in England.

On-the-spot doorstep tests, home testing kits and mobile testing units will be used to try to reach 80,000 people in eight specific areas.

The efforts are to track down and stop the spread of the more infectious South African variant of the virus.

Variants are a totally normal part of the life of a virus, as it adapts and changes according to conditions. There are several variants of coronavirus already and this version was first recorded in South Africa, but variants have been found here in the UK too.

The health secretary Matt Hancock said he wanted to "come down hard" on the variant and that "finding every case" is the goal, with everyone over 16 in the targeted areas urged to take a test, whether they have symptoms or not.

A variant is a different version of a virus - all viruses change and mutate so this is not unusual.

So far thousands of new variants have been found across the world, but health experts are currently focused on versions found in the UK, South Africa and Brazil.

Scientists are studying these mutated versions to understand what makes them different, and whether those differences may make them better at spreading between people, for example, or if it means changes need to be made to the vaccines that have been developed.

So far over 100 cases of the variant have been found which - like the previous versions - are thought to be more contagious, although not more deadly. Eleven of the cases of the South African variant had no link to foreign travel, prompting concerns it is spreading in the community.

Dr Susan Hopkins from Public Health England said the existing vaccines may offer less protection against the South African variant, although they still offer a good level of immunity.

In most of the areas, home testing kits are being delivered and collected, while some are also providing mobile testing sites.

In Kent, police, council workers, fire-fighters and other agencies will visit homes to carry out on-the-spot tests of everyone in the household.

Mr Hancock also said it was "absolutely vital" that people in these areas where cases of the variant had been identified minimise all social contact.

Mass testing has previously been used in Liverpool, using lateral flow tests, where more than 200,000 people were tested in November, detecting 800 asymptomatic cases.

The surge testing being deployed in the eight areas where the South Africa variant was detected will, however, offer the more accurate PCR tests to people who need to leave home for work or other essential purposes.