1:600 "D" class cruiser Diomede, 1943. Note 'A' 6" gun is in a turret ( in Diomede only ) to allow working in heavy seas © Andrew Arthur

This class was similar to the "C" class, but lengthened by 22 feet to allow the addition of a 6" gun between the bridge and number 1 funnel, although this was a dubious gain - it could only fire on the broadsides, and had no aft or for'ard arcs of fire.
The Danae, Dauntless and Dragon were ordered first - and before the improved "C" class, the Capetowns. Thus, they lacked the trawler bows of the later ships, and consequently were rather wet for'ard. The later Despatch and Diomede had their beam increased by 1/2 a foot to improve seakeeping, and only Dauntless and Dragon were fitted with the planned hangar and catapult built into the bridge, the others all recieving flying off platforms aft.
The original AA armament was that of the Capetowns, of two 3" and two 2 pound AA guns. However, the last three units, Despatch, Durban and Diomede had 4" instead of 3" guns, and in addition, Diomede had "A" 6" gun in a turret to allow working in adverse weather.
Between the wars refits standardised the armaments of the class, all having two 4" instead of 3", a 4" gun replaced the 2 pound guns aft, and the latter were moved into the bridge wings. All catapults and flying off platforms were also removed.
Early war, SW type 273 RDF was added, and either six 20mm cannons were added and the 2 pdr's retained, or eight 20mm were added and the 2 pdr's removed. These were carried in the wings (2) if the 2 pdr's were not retained, two aft of "Q" turret and a further two aft of "R" turret. The final pair were added on the quarterdeck.
In 1943, Danae and Dragon had the useless "Q" and the two forward 4" removed, and two quad pom-poms and their directors added between the bridge and funnels. Danae had the aft 4" temporarily replaced by a third pom-pom, but later both her and Dragon carried the twin 4" AA turret, had their torpedoes removed and their after superstructures cut away.
During 1942, Delhi went to the USA for a refit as an AA cruiser, and returned with a new brige, similar to the Arethusa class, had tripod masts and all 6", except "Q" which was removed, were replaced by single turreted USN 5" 38 calibre DP guns, controlled by fore and aft RDF fitted USN Mk.37 directors. For close defence, two quad pom-poms and their directors were added abreast the fore-funnel, two twin 20mm AA were added in the wings, and six single 20mm's were added along the aft-upper deck. SW type 273 was fitted just ahead of the mainmast, AW type 291 was carried on the foremast, and the directors carried AR type 285 (Mk.37) and AR type 282 (pom-pom).
In 1944, Dragon and Durban were expended as breakwaters for the "mulberry" harbours of the D-day beaches, Despatch was re-armed with six 40mm AA as a depot ship, and Dragon, later Danae as Conrad, was loaned to the Free Polish Navy.