But will it go ahead?
So far, yes. From the Cadogan Hall website today:
This is not a socially distanced performance
As the government considers a move away from social distancing measures, such as the two-meter rule, it is our greatest hope that this event may be staged to a full-capacity audience.
Naturally, this is entirely conditional on the country’s ability to keep the virus under control. Therefore performances that have been sold to a full-capacity audience may be postponed or cancelled should distancing measures remain in place.