On 4 September 1929, the ship was transferred to the Mediterranean Fleet as the flagship of the 3rd Cruiser Squadron, which was commanded by her first captain, Barry Domvile. She remained in the Mediterranean until 1932. She became a gunnery training ship on 18 December 1933 and continued in that role until 1939. In 1935, she was one of four Royal Navy ships featured in the British film "Brown on Resolution", where she played a German battlecruiser. In July 1939, a few months before the outbreak of the Second World War in Europe, she began a conversion into an anti-aircraft cruiser at Chatham Dockyard. This consisted of replacing all of her six-inch guns with eight QF 4-inch (102 mm) Mk XVI dual-purpose guns in four twin-gun turrets, in the positions formerly occupied by Nos. 1, 3, 4, and 5 six-inch guns. A quadruple mount for the two-pounder Mk VII "pom-pom" light AA gun was installed in No. 2 gun's position. Quadruple Vickers AA machinegun mounts replaced the three-inch guns and her torpedo tubes were removed. Her masts were cut down and her existing fire-control systems were replaced by a pair of High-Angle Control System Mk III systems and a pom-pom director. A Type 279 early-warning radar was also installed. To counter the additional weight high in the ship, of ballast was added. Although the weight of the ballast alone was more than that of the new equipment, it increased her metacentric height from at deep load.