Omicron variant: the new Covid rules set out in Boris Johnson's speech

Boris Johnson has taken swift action to try to tackle the omicron variant of Covid-19 that is causing significant concern among scientists.

Two cases have already been identified in the UK - in Nottingham and Brentwood, Essex - and they are believed to have been contracted in southern Africa.

Flanked by England's Chief Medical Officer, Chris Whitty, and the Chief Scientific Officer, Patrick Vallance, the Prime Minister held an unexpected press conference on Saturday and announced a series of tighter restrictions.

Here is what he announced:

1. Anyone arriving in the UK will be asked to take a PCR test for Covid-19 on the second day and must self isolate until they provide a negative test.

2. All contacts of people who do test positive with the suspected variant will have to self-isolate for 10 days.

3. The rules on face coverings are changing. They will become compulsory on public transport and in shops, but not including hospitality.

Mr Johnson told the press conference: "We're not going to stop people travelling, I want to stress that, we're not going to stop people travelling, but we will require anyone who enters the UK to take a PCR test by the end of the second day after their arrival and to self-isolate until they have a negative result.

"Second, we need to slow down the spread of this variant here in the UK, because measures at the border can only ever minimise and delay the arrival of a new variant rather than stop it all together.

"We will require all contacts of those who test positive with a suspected case of omicron to self-isolate for 10 days regardless of your vaccination status.

"We will also go further in asking all of you to help contain the spread of this variant by tightening up the rules on face coverings in shops and on public transport."

He continued: "We need to bolster our protections against this new variant.

"We don't yet exactly know how effective our vaccines will be against omicron but we have good reasons for believing they will provide at least some measure of protection.

"If you're boosted, your response is likely to be stronger so it's more vital than ever that people get their jabs and we get those boosters into arms as fast as possible.

"From today we're going to boost the booster campaign, we're already planning to do six million jabs in England alone over the next three weeks and now we're looking to go further.

"The Health Secretary has asked the JCVI (Joint Committee on Vaccination and Immunisation) to consider giving boosters to as wide a group as possible as well as reducing the gap between your second dose and your booster."