Coronavirus latest news: New Covid variant has already spread across the UK, Sir Patrick Vallance warns

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Watch: What is the new Covid variant?

The new variant of Sars-Cov-2 has already "spread around the country", the Government's chief scientific adviser has said, warning that more regions could be put under Tier 4 restrictions in the coming weeks.

"It's localised in some places but we know there are cases everywhere, so it's not as though we can stop this getting into other places, there's some there already," Sir Patrick Vallance told a Downing Street press conference.

"The message has been very clear and, I think I want to reinforce it, is stay local. People shouldn't be travelling around the country at the moment... it's got to be taken incredibly seriously."

Sir Patrick added that the tiered system will be vital to help contain Covid-19, but as the new variant "spreads easily" it is likely that "measures are going to need to be increased in due course not reduced".

This is partly because he expects there to be an "inevitable" increase in cases over the coming weeks, as people mix at Christmas. "I think it is the case that this will spread more," he added.

Watch: In full - Boris Johnson gives coronavirus update

His comments come as the Government's New and Emerging Respiratory Virus Threats advisory group (Nervtag) told a Science Media Centre briefing on the new mutant variant that cases outside of Tier 4 in London and the south east of England "are increasing at similar rates" to those in affected areas.

Experts have also said the variant it has a "transmission advantage" over other strains of the virus, meaning it is likely to become the dominant variant in the UK and across the world.

However, World Health Organisation director-general Dr Tedros Adhanom Ghebreyesus said there was "no evidence" the new strain was "more likely to cause severe disease or mortality".

Elsewhere, regional public health directors in Manchester and the West Midlands urged anyone who travelled from a Tier 4 area or Wales to self isolate upon their arrival and "assume" they have the new Covid-19 variant.

Follow the latest updates below.

A nurse holds an 11-day-old baby boy infected with Covid-19, at the intensive care unit of the Prof. Dr. Feriha Oz Emergency Hospital - AP Photo/Emrah Gurel

Lorries parked on the M20 near Folkestone, Kent, as part of Operation Stack after the Port of Dover was closed and access to the Eurotunnel terminal suspended following the French government's announcement that it will not accept any passengers arriving from the UK for the next 48 hours - Steve Parsons/PA Wire

People wearing masks walk past people dining in plastic bubbles used for social distancing amid the coronavirus pandemic - Alexi Rosenfeld/Getty Images

Long queue of motorists who are entering Queensland from New South Wales through the border checkpoint. Queensland has closed its border to greater Sydney residents as a cluster of Covid-19 cases continues to increase. Queensland residents returning from Sydney have until 1am on Tuesday get home. - Regi Varghese/Getty Images

People under a Christmas light display on Carnaby Street in London - Kirsty O'Connor/PA Wire

REUTERS/Matthew Childs - REUTERS/Matthew Childs

Steve Parsons/PA - Steve Parsons/PA

Steve Parsons/PA Wire - Steve Parsons/PA Wire

Vehicles queue as medical personnel administer tests at a drive-through COVID-19 testing centre in Sydney - Reuters