British Documentary Movement
While the British documentary film movement had its roots in the Soviet propaganda tradition, it developed during the Great Depression, producing state-sponsored films that were both idealistic and practical in their treatment of social issues and problems. At the same time, there were many socialist, left, progressive, or workers' films. John Grierson not only believed that the documentary film should provide a "creative treatment of actuality", but he also realized that the state could use film and other media to control and manipulate the audience. The political implications of Grierson’s approach seem Marxist: film was to be used to inform people about the material and political causes of vast social problems. But, in fact, he avoided Marxist dogma, and produced films that were intended not only to educate, but also to praise and illuminated the human condition. In this sense, the practical and aesthetic goals of the British documentary film movement were balanced much more effectively than should at first have seemed possible. Although ist primary role was as a source of informa-tion and education primarily on behalf of government functions, the movement also offered filmmakers an unparalleled scope for creative experimentation.
From 1928–1937, John Grierson's leadership was undoubtedly the single most important influence on the development of the British documentary film. His insistence on propaganda in the public interest, his support of cinematic experimentation, and his enlightened supervision of hundreds of major documentary films brought the movement to its high point of maturity in a relatively short time.
SOURCES
Richard M. Barsam. Non-fiction Film. A Critical History. p. 89, 95
http://www.nfb.ca/e/highlights/john_grierson.html