Would Britain begin building River-, Loch-, and Bay-class frigates before World War II in a larger-fleet scenario?
Short answerProbably not in their wartime form; a prewar program would more likely continue Hunt-type escort destroyers built to full naval standards.
NotesA peacetime Royal Navy preparing before the war would probably continue building Hunt-class escort destroyers instead of ordering the later River, Loch, and Bay frigates early. Those frigates emerged as wartime mobilization designs, one step above corvettes and suited to construction on broader commercial lines. A prewar program would use full naval standards and yards. The service would still seek convoy escorts, but the production environment points toward a more conventional escort destroyer or sloop.