From this came our insistence on the drama of the doorstep" (cited by Hardy 14-15). Grierson also notes that the early documentary filmmakers were concerned about the way the world was going and wanted to use all the tools at hand to push the public towards greater civic participation.

With the success of Drifters, Grierson was able to further his ideas, but rather than directing other films, he devoted his time to building up a film unit and training its members, gathering young men of like mind, including Basil Wright, Arthur Elton, Stuart Legg, Paul Rotha, John Taylor, Harry Watt, Donald Taylor, Edgar Anstey, and more. these men were "united by a common enthusiasm and a common aim" (Hardy 15). The E.M.B. Film Unit in the early 1930s had an atmosphere that was energizing and inspirational, with Grierson being one of the main reasons for this state of affairs. He also saw the documentary film as basically a British movement, and certainly Britain was welcoming to him and the movement and offered considerable support.

The E.M.B. Film Unit grew two people to over thirty by 1933 and moved from a cellar in the Charing Cross Road to an attic in Wardour Street, and later to an office in Oxford Street. The unit produced over a hundred films. Hardy says that the most memorable of these were films immediately after Drifters and were films that demonstrated Grierson's quality as a producer. These films included Industrial Britain, made by Robert Flaherty,; Wright's Country Comes to Town, on London's market services, and O'er Hill and Dale, an account of a day in the life of a Border shepherd; and Elton's Upstream, about salmon fishing in Scotland, and Shadow on the Mountain, on Professor Stapledon's pasture experiments at Aberystwyth. These were experimental films were Grierson's first contribution to the task of bringing Britain and the British Commonwealth. The documentary film was now clearly a movement.

Grierson was working as a promoter of the unit to Whitehall, to produce new films with the day-to-day progress of perhaps twenty films at a time, caused to be established the Empire Film Library at the Imperial Institute, and to serve as the primary voice promoting the documentary idea. He also lectured all over the country before learned bodies, film societies, discussion groups, universities, conferences, and schools, and at the same time he wrote tirelessly about documentary theory. Much of what he wrote was published through Cinema Quarterly, the Edinburgh journal founded by Norman Wilson and Forsyth Hardy. Grierson later expanded this into a monthly magazine called World Film News. As part of his program, he enlisted the active support of critics and journalists in London and also in the English provincial cities and in Scotland. The Empire Marketing Board was dissolved in 1933, but the documentary film movement was well established by then and survived:

Already members of the unit had made films, under Grierson's guidance, for one or two Government departments and a number of enlightened industrial undertakings.

But it was important that the unit Grierson had established should continue as a training school and as a clearing-house for documentary theory and practice. Hardy 17)

Grierson experimented as much with new techniques as with new subject-matter during this time.

The G.P.O. Film Unit he opeated for the Post Office had acquired its own sound equipment, and Grierson used this to demonstrate his belief that "the soundtrack need not simply provide the obvious accompaniment in dialogue and music to the visuals but could make an individual and different contribution" (Hardy 17), as was shown in films like Song of Ceylon, Night Mail, Pett and Pott, and Coal Face. The use of sound in these films was far in advance of contemporary studio thought or achievement. Cavalcanti was brought in from France as a guest producer and left the his signature on many of the G.P.O. films.

Among those participating in some way were W.H. Auden, Walter Leigh, and Benjamin Britten. Hardy cites these films as representing "the most considerable achievement yet recorded in the imaginative use of sound, and they did much to keep the G.P.O. Film Unit in the foreground of public attention in Britain and to win recognition for British cinema abroad" (Hardy 18).

Grierson as producer did not impose any rigid requirements on the filmmakers and let the style of the films be influenced largely by the subject-matter. This was part of his view of the way subjects should be treated by this form of filmmaking. He notes that at one level, the vision of the documentary may be observation was made more and more an integral part of the films. This emphasis could be seen in the G.P.O. production We Live in Two Worlds and Forty Million People and even more in the work done outside the Unit by the directors Grierson had trained, with such films as Workers and Jobs, Housing Problems, and Enough to Eat, and evenmore notably in such later films as the Londoners, Children at School, to-day We Live, and Wealth of a Nation, all films sponsored by the many industries and organizations outside the Government and which were now beginning to use film on a large scale, films produced by the rapidly growing number of documentary units founded by members of the original Grierson group (Hardy 18-19).
Grierson resigned from the G.P.O. Film Unit in June, 1937, at a time when there was already a larger volume of documentary production outside than inside Government sponsorship. What was needed was a central advisory body, and Grierson then set up Film Centre in association with Arthur Elton, Stuart Legg, and J.P.R. Golightly in order to provide a consultative and policy-forming center for a movement. Film Centre was not a producing unit but a unit that undertook investigation and research, offered advice on the use of documentary film, and supervised production, with Grierson acting as a fount of ideas and initiative. One example of his work at this time involved the Films of Scotland Committee, with the aim of the projection of the country in terms of film. To improve the image of Scotland seen in films, Grierson drew up a production program of seven films that described the country's character and traditions, its economic planning for industrial development, its agriculture, education, and sport. The films were produced by different units and used different styles, but all are marked by Grierson's production genius so that they remain a unique and remarkably comprehensive record of a country's achievement and outlook. Grierson saw the Scottish films as part of what he called "the battle for authenticity" that reached a peak in the year before the outbreak of war.

Hardy notes,

Documentary in Britain had not achieved its comparative freedom in social comment without meeting considerable opposition. Most of this had been concealed from the public and much of it had been overcome by Grierson's tenacity and integrity of purpose. It was brought into the open, however, by the selection of films made for the New York World's Fair. The selection was in the hands of the British Council's Film Committee... And the films chosen to represent Britain reflected the Council's belief in the importance of tradition and ceremonial. Documentaries dramatizing Britain's struggle to solve her social and industrial problems were excluded. The resulting controversy was bitter, touching as it did the core of all that Grierson stood and had striven for. He had the support of the press in Britain and the United States and ultimately, in response to a direct request from the World's Fair for the authentic documentaries of Britain, the films were sent from Film Centre and shown, not as part of the official British exhibit, but in the Arts and Science Pavilion. Grierson's purpose was achieved; but I feel that the struggle and all that it implied had something to do with his ultimate decision to move into a fresh field. (Hardy 20)

In 1937, the British Government created the Imperial Relations Trust, an organization similar in some ways to the E.M.B., and in 1938, Grierson was commissioned to visit Canada, Australia, and New Zealand to investigate the possibilities of film production in those locations. He completed his Canadian survey in 1938 and visited Australia in 1940. When World Wear II started, he was in North America. In October 1939, the Canadian Government made…