Block by block, Adam Curtis’ astonishing history uses archival footage to build a narrative of societal collapse, political opportunism, corruption and identity crisis in the USSR’s final hour. Curtis mines the mundane footage that most TV producers would fast-forward through, sharing English lessons at a beauty pageant, a young waif begging for rubles in the streets, the unrelenting churn of a toothbrush factory and scientists, wrapped in plastic and tape, trying to fix the Chernobyl reactor after meltdown. In lesser hands, the collage might seem random or diffuse.