There are two definitive proofs that Harold Pinter utterly rejected his Jewish roots. 1 - because he said so most clearly in an interview on that topic and 2 - he was not buried in a Jewish cemetery.
It is unusual for a well-known public figure not to have a place of burial / cremation / other noted in or soon after the obituary. It is impossible to find (10 Jan 2021) any hint, direct or oblique, with regard to Prof. Leo Panitch. Nu?