In the first photo, it’s a shame that Klemperer’s left-arm is covering the leader’s face, it could be Manoug Parikian (Philharmonia leader 1949-57), although it’s easy to identify Hugh Bean (a future PO leader) to his left.

As a postscript, I have no real memory of writing this…

https://philharmonia.co.uk/who-we-are/our-history/

… but as I am credited, I must have done!