That's all according to a defector (which brings us back to the original conversation) and a member of MI5. The notes that form the basis of those claims are still classified.
I was born in USSR, and lived in it enough to be able to reassure you it was not possible to publish a book there in 1974 just because you decided it for yourself. Even authors of fairytales were forced to make ideological "corrections", not to mention anything even distantly political.