Rotha's companies Paul Rotha Productions and Films of Fact had not been short of work. Between 1942 and 1945 Rotha produced eighteen issues of his newsreel Worker and Warfront for screening to war-industry workers, pushing out five final issues in 1945. To these Alwyn contributed title music, breaks, and end titles. The company was also occupied with documentaries. Alwyn wrote the scores for two, and although release was delayed until the following year they reflect the national mood of early 1945.

Rotha's intention in Total War in Britain (1946) was to show that central planning was as important to winning the peace as it was the war. At times its stridency verges on the hysterical. It commences with a depiction of the front pages of European newspapers circling around the screen, against which the titles appear word by word : “Total – War – in – Britain”, a chord beating against each word and ascending in scale. The musical composition then adopts a deferential grandiose tone as a caption acknowledges a government source for the statistics of D-Day mobilisation. The titles set the technical style, which is mainly a sophisticated variant of what Rotha essayed in World of Plenty, with its origins dating back a further seven years to New Worlds for Old: that is to say, compilation pictures and graphics choreographed with music and soundeffects of all kinds. Alwyn obviously enjoys Rotha's challenge, his score moving from pathos to the ceremonial, with many short cues, drum rolls, drumbeats, explosions, tambourines, recorded cymbals played backwards, and so on. The film ends as hysterically as it begins, with the commentator John Mills uttering “Fulfilment!” against shots of the D-Day landings, and Alwyn's Elgarian theme climaxing over British newspaper headlines such as “This Their Final Hour”. Although today its contrived style is out of fashion, the film's meticulous balance of music, effects, and pictures holds a fascination, and even perhaps a few technical lessons.

The second of Rotha's 1946 releases to which Alwyn contributed, Land of Promise, received high praise. RM of the Monthly Film Bulletin called it “an important film in the development of British Documentary”, although time has tempered that judgement.