Don't just do something, sit there. - TNH
There seem to be very few pictures of Bertrand Russell with a beard - could it possibly be the Conway Hall?
I was wondering what it was that you went to see and had a look at the archive.
https://www.conwayhall.org.uk/whats-on/archived-events/
Might it have been the delightfully named Arsehole Quartet on the 25th Feb?
Or the Pete Tong Duo on the 4th?
In the Sotadic Zone, apparently.