Why interwar sloops were industrial training ships

Hull fabrication, turbines, gearboxes, shafts, and destroyer-calibre guns are the difficult industrial elements. Torpedo launchers are topside equipment that can be added when a wartime destroyer design is required. A later design aside makes that conversion path concrete: reserve deck space could carry a peacetime crane and boats, then accept a swivel torpedo mount in war. A continuous sloop programme would therefore preserve the workforce and supplier network needed for wartime destroyers. In peacetime the same ships could perform patrol, escort, hydrographic, lighthouse-support, coastguard, and reserve-training duties.