Courtesy CNN

London (CNN)Parts of Britain will go back into lockdown during Christmas after a newly identified strain of Covid-19 proved to spread more quickly than previous strains of the virus.UK Prime Minister Boris Johnson on Saturday announced a series of stricter coronavirus restrictions, tightening rules around household mixing that were due to be relaxed over Christmas in London and southeast England. The PM broke the news Saturday that London and the southeast of England, where cases are surging, will go into Tier 4 restrictions, similar to a lockdown, on Sunday.”The spread is being driven by the new variant of the virus,” Johnson said in a hastily called press conference. “It appears to spread more easily and maybe up to 70% more transmissible than the earlier strain.”England’s chief medical officer, Professor Chris Whitty, warned Saturday that a newly identified variant of Covid-19 “can spread more quickly” than previous strains of the virus. Analysis from Luke McGee

It was only on Wednesday that Boris Johnson was attacking the leader of the opposition, Keir Starmer, for wanting to “cancel Christmas,” before delivering a press conference in which he informed the public that if they wanted to celebrate Christmas with loved ones, on their head be it.

This sudden change of policy just days before Christmas and three days before Johnson’s special Christmas rules came into effect is a political minefield for a Prime Minister whose handling of the pandemic has been attacked by all sides.

For his opponents, a U-turn this late in the day will typify Johnson’s habit of resisting taking hard action, which they attribute to his reluctance to be the bearer of bad news. Critics can reasonably point to multiple examples of the PM ignoring Starmer’s calls to introduce stricter measures, only to do exactly that days or weeks later.

For his critics inside the Conservative Party who have been uncomfortable with impinging on people’s freedoms and liberties since the start of the pandemic, this is more evidence that Johnson is an indecisive leader beholden to his scientific advisers.

And to the public, whether they believe it was down to his inaction or indecision, Johnson will now always be remembered as the PM who canceled Christmas for so many. Downing Street must now pray that this urgent action is enough to prevent what many suspected would happen: thousands more deaths on top 65,000 the UK has already experienced.”This is now spreading very fast,” Johnson warned. “It is with a very heavy heart that I say we cannot continue with Christmas as planned.”Johnson outlined that in areas under the toughest restrictions, there will be no possibility for household mixing over Christmas. In areas under Tier 3, mixing will now be restricted to Christmas Day.Alert Level 4 restrictions will be brought forward to apply across Wales from midnight, the country’s First Minister Mark Drakeford announced Saturday, meaning that “festive bubbles” can be formed only on Christmas Day, PA Media reported. Under Alert Level 4, people must stay at home except for very limited purposes, and must not meet with other households or meet people they do not live with, while many businesses are required to close.As recently as this week, Johnson reiterated his pledge to relax rules over the Christmas period, allowing up to three households to mix for five days. But as of Saturday, the entire nation is being asked not to travel and those under the highest level of restrictions, will not be allowed to travel abroad except for work purposes.Keir Starmer, leader of the opposition Labour party, criticized the government’s handling of the crisis, saying: “Many people will be heartbroken by the news that their Christmas plans are being ripped up.”I’m really frustrated because I raised this with the Prime Minister on Wednesday, and he dismissed that. He went on to tell people to have a ‘merry little Christmas,’ only three days later, to rip up their plans,” he said on Sky News.According to Whitty, the new variant is responsible for 60% of infections in London, which have nearly doubled in the last week.Earlier, he said “urgent work” is underway to establish whether the new strain, prevalent in the southeast of England, can cause a higher mortality rate.”There is no current evidence to suggest the new strain causes a higher mortality rate or that it affects vaccines and treatments although urgent work is underway to confirm this,” Whitty said in a statement.Boris Johnson is facing two hellish weeks. Critics fear his weak leadership could seriously harm the UKAs with other new variants or strains of Covid-19, this one carries a genetic fingerprint that makes it easy to track, and it happens to be one that is now common. That does not mean the mutation has made it spread more easily, nor does it not necessarily mean this variation is more dangerous.Multiple experts in the genetics and epidemiology of viruses are noting that this one could be just a “lucky” strain that’s been amplified because of a superspreader event; it could be the mutation somehow makes it spread more easily without causing more serious illness; or it could just be by chance.The government’s scientific advisory group for Covid-19 has also warned the new strain is a “real cause for concern,” and called for urgent action. On Twitter, Jeremy Farrar said, “Research is ongoing to understand more, but acting urgently now is critical. There is no part of the UK & globally that should not be concerned. As in many countries, the situation is fragile.”Whitty also urged people to take more precautions. “Given this latest development it is now more vital than ever that the public continue to take action in their area to reduce transmission,” he said.