London will move into England's highest tier of COVID-19
restrictions, the government said on Monday, citing increased infection rates that may be partly linked to a new variant of the coronavirus.
Health Secretary Matt Hancock said more than 1,000 cases of the new variant had been identified, mainly in southeastern England.
Although there was currently nothing to suggest the new strain was likely to cause more serious disease or that it would not respond to a vaccine, Hancock said that it could be contributing to higher infection rates.
"Over the last week, we've seen very sharp, exponential rises in the virus across London, Kent, parts of Essex and Hertfordshire," Hancock told the House of Commons in a statement, referring to counties near London.
"We do not know the extent to which this is because of the new variant, but no matter its cause, we have to take swift and decisive action," he said, announcing that the entire capital and some neighbouring areas would go into "High Alert" level.
Earlier this month, the government implemented a three-tiered system of restrictions in England to try to keep a second wave of the virus under control after a month-long national lockdown. More than 40% of citizens were placed in the highest risk category.
However London, whose 9 million people and world-leading financial centre make it the engine of the British economy, is currently only in the middle tier of restrictions.
The tougher Tier 3 restrictions will come into force in the capital from 0001 GMT on Wednesday. England's Chief Medical Officer Chris Whitty said the detection of the new variant was not the reason for the decision to put London in Tier 3 - the reason was the sharp rise in infections.
Whitty said there was no evidence that the clinical outcome was different for the new variant.
"There are many variants. It just happens that this one has quite a few more mutations than some of the other variants, so that's the reason why we've taken it particularly seriously," Whitty said during a news conference with Hancock.
The World Health Organization (WHO) confirmed that Britain had reported the variant, but added that mutations were not uncommon, a view echoed by several other experts.
Martin Hibberd, Professor of Emerging Infectious Diseases at the London School of Hygiene & Tropical Medicine (LSHTM), said the reports were "not surprising and it was too early to say how important it is yet," adding it was believed that one previous mutation had let the virus to spread more easily.
The main difference between England's top alert levels is that bars and restaurants, which can stay open under certain conditions in Tier 2, must close their doors in Tier 3 and can only operate takeaway services.
There are also additional curbs on socialising in Tier 3, but workplaces and schools are told to remain open.
"Moving into Tier 3 before Christmas will be deeply disappointing for Londoners, and a terrible blow to the capital's hospitality, leisure and cultural sectors," said John Dickie, Director of Strategy and Policy at business campaign group London First.
London was one of the first parts of the country to be hit by the coronavirus during the initial peak between March and May, but until recently a second wave has been more concentrated in northern and central England.
Data published last week showed case rates per 100,000 people in London stood at 191.8, putting the city ahead of regions that have stricter rules in place, such as the West Midlands.
Based on that data, the government raised concerns about the spread of the virus in London schools and announced a programme of mass testing. Two London boroughs, Greenwich and Islington, have unilaterally decided to close their schools.