Whwn I was a kid in post-war London the Communist Party was still in full swing. One has to remember that the House of Commons reverberated to 'The Red Flag' after Atlee's election victory in 1945. The Daily Worker was as common as the Daily Mirror in the shops. In the sixties The Young Liberals was effectivly a Communist Front organisation.
It was fashionable for the intelligentia before the war to join the CP as Russia was seen as the cure for the world's troubles. Nowadays they join the Green Party or Friends of the Earth.