During the Second World War Walton was exempted from military service on the understanding that he would compose music for wartime propaganda films. In addition to driving ambulances (extremely badly, he said), he was attached to the Army Film Unit as music adviser. He wrote scores for six films during the war – some that he thought "rather boring" and some that have become classics such as "The First of the Few" (1942) and Laurence Olivier's adaptation of Shakespeare's "Henry V" (1944).