A shelter was added for the gun crews between each pair of guns as it was recognised that in wartime the crews would spend a lot of time closed up at action stations and would rapidly fatigue in the open gun mountings. "Galatea" received similar alteration before the outbreak of war. The light armament consisted of eight 0.5-inch Vickers machine guns in two quadruple mountings. A rotating catapult for a float plane and a derrick were fitted between the funnels. It had been intended to carry a second aircraft aft, but in the end this never happened. "Aurora" completed without aircraft facilities, and had a deckhouse for accommodation in lieu for service as commodore. "Aurora" received an unrotated projectile (UP) mounting and eight QF 2-pounder Mark VIII in two quadruple mountings Mark VII in the summer of 1940. Radar Type 284 was added to the main armament director for taking ranges and bearings, and Type 280 air warning at the mastheads was added in April 1941. In August of the same year she received six single 20 mm Oerlikons and two quadruple 0.5-inch machine guns. In 1943 she received Radar Type 282 on the 2-pounder "pom-pom directors". "Galatea" had extra plating added amidships after completion to reduce wetness and to protect the boats. She landed her catapult during a refit between October 1940 and January 1941, when she received two quadruple 2-pounders and eight single 20 mm Oerlikons, as well as Type 279 air warning radar added at the mastheads. "Arethusa" had received two quadruple 2 pounders and radar by April 1941, and landed the catapult. Later the same year, two UP mountings and four single 20 mm Oerlikons were added. The former were removed in the spring of 1942, as were the single 4 in mountings (replaced by twins as per her sisters) and a further four 20 mm Oerlikons added. Radar Type 286 air warning was landed and radars Type 273 centimetric target indication, Type 281 air warning, Type 282 on the 2-pounder directors, Type 284 on the main armament director and Type 285 on the HACS directors were fitted. Three additional 20 mm Oerlikons were added by October 1942. Between March and December 1943, while under repair in the United States, the 2 pdr were supplanted by quadruple 40 mm Bofors mountings Mark II, three single Oerlikons by four twin power-operated mounts Mark V and had the radar fit modernised.