The Active-class scouts were too slow for flotilla leadership and increasingly unsatisfactory even for scouting. A faster cruiser needed space for machinery, boilers and fuel, which encouraged a larger hull and a heavier gun battery. The 1910 Town class illustrates what roughly 1,500 additional tons could buy: 6-inch guns and protection at a similar 25-knot speed. Later Arethusa, C, Danae and Emerald classes gained speed, with the Emeralds reaching 33 knots in this comparison. By that stage, the destroyer leader had become a distinct large-destroyer solution while the light cruiser developed its own fighting role.
Chapter · 23:30-25:58
Why light cruisers grew away from destroyer leadership
Machinery, armament and protection pushed light cruisers along a different design path from large destroyer leaders.