The high-angle directors and rangefinder and their platform were replaced by a new circular platform for the High Angle Control System (HACS) Mk I director in May–June 1930. By March 1934, the single two-pounder guns and the starboard torpedo director were removed and replaced by a single octuple two-pounder "pom-pom" mount on the starboard side of the funnel. It was provided with a Mk I director mounted on the bridge roof. In 1934–1935, "Nelson" was fitted with a pair of quadruple mounts for Vickers AA machineguns that were positioned on the forward superstructure. The ship was also fitted with a crane to handle a Supermarine Seagull biplane flying boat carried for test purposes; the crane was retained after the end of the trials. Sometime in 1936–1937, she received her portside "pom-pom" and its director. In addition gun shields were fitted to the 4.7-inch guns although they were removed by March 1938. During her refit from June 1937 to January 1938, "Nelson" had her high-angle director tower reinforced and enlarged to accommodate a pair of HACS Mk III directors and new non-cemented deck armour was installed. Like the aft deck armour, it was at the level of the bottom of the armour belt, and extended forward from the front of the citadel almost to the bow; ranging in thickness from close to the citadel to near the bow.