The founding principles of the movement were based on Grierson's views of documentary film.
The unit was headed by John Grierson, who appointed apprentices such as Basil Wright, Arthur Elton, Edgar Anstey, Stuart Legg, Paul Rotha and Harry Watt.
These filmmakers were mostly young, middle-class, educated males with liberal political views.
Whereas previously the documentary film movement had been located in a single public sector organisation, it separated in the late 1930s into different branches, as filmmakers explored other possibilities for developing documentary film.
In 1939, Grierson left Britain to work with the National Film Board of Canada, where he remained until 1945.