How the Royal Navy reached the six-inch triple turret

Where did the Royal Navy's six-inch triple turret come from?

It emerged from late-1920s development and earlier Leander and Arethusa proposals before the Town class adopted four mature triple mounts.

The Royal Navy began studying triple six-inch turrets in the late 1920s as a practical route to greater cruiser firepower. Mixed double-and-triple arrangements were considered for the Leander class, while an Arethusa design nearly received a single triple mount forward. Readiness and maintenance concerns delayed adoption until the mechanism was mature enough for the Town class. The Towns then carried four triple turrets, although the Edinburgh design process also examined and rejected quadruple mounts.