London is set to move into Tier 3 from Wednesday, December 16 as a result of the rise in coronavirus case rates.
Health secretary Matt Hancock set out the move, which also affects parts of Essex and Hertfordshire, in a House of Commons statement this afternoon (Monday, December 14).
MPs briefed on the plans via a call in advance of the announcement said a sharp rise in cases meant Mr Hancock was unable to wait until the scheduled review of England's tiers on Wednesday.
One MP said they were told that cases are doubling every seven days in the capital.
It follows warnings from London Mayor Sadiq Khan that Tier 3 restrictions - which will involve the closure of pubs and restaurants except for takeaway and delivery services - would have a "catastrophic" economic impact.
Mr Hancock revealed that the spread in the region could be down to a new strain of Covid-19, adding: "Over the last few days, thanks to our world-class genomic capability in the UK, we have identified a new variant of coronavirus which may be associated with the faster spread in the south of England."
He told the Commons: "Initial analysis suggests that this variant is growing faster than the existing variants.
"We've currently identified over 1,000 cases with this variant predominantly in the south of England although cases have been identified in nearly 60 different local authority areas.
"Over the last week, we've seen very sharp, exponential rises in the virus across London, Kent, parts of Essex and Hertfordshire.
"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."
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