After nearly twenty years as a major, Berryman was promoted to brevet lieutenant colonel on 12 May 1935. Promotion to substantive rank, which carried the rank's pay as well as status, occurred on 1 July 1938, when he became Assistant Director of Military Operations at Army Headquarters. From December 1938 to April 1940 he was General Staff Officer Grade 1 (GSO1) of the 3rd Division. The slow rate of promotion of regular officers in the inter-war years fostered a sense of injustice and frustration among officers with good war records who found themselves outranked by Militia officers who had enjoyed faster promotion.