The disease is spreading quickly in every corner of the city, he cautioned Londoners.
While London has initially been placed in the ‘medium’ category of the government’s new three-tier system for local lockdowns “this could change very quickly - potentially even this week," a spokesman said.
Just hours early Mr Khan had issued a rallying call to everyone in the city, telling Londoners “we can turn this around”.
Aides to the mayor have been concerned at the spread of the virus in the city for weeks, leading to speculation that Londoners could be told to work from home.
In the end ministers changed their guidance to advise everyone who could do their job away from the office to do so.
From Wednesday all bars, pubs, gyms, casinos and betting shops in Merseyside will have to close under the new system.
The area is the only one in the country, so far, to be classified as at “very high” risk.
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