London is moving into tier 3 from Wednesday.
Ministers and officials are said to be "deeply concerned" about a sharp rise in Covid-19 cases across the capital.
Around three quarters of the 32 boroughs have seen a rise in cases, particularly among secondary school-age children.
It has been confirmed that London's theatres will have to cease performances from tomorrow night (Tuesday 15th).
All West End shows with performance dates from Wednesday morning will have to postponed due to government regulations regarding risk mitigation.