The Bittern hull was a design ancestor of both Black Swan-class sloops and Hunt-class destroyers despite visible modifications between classes. Hunts were called destroyers because they could exceed 20 knots, although Black Swans could also reach that threshold. Before computer-aided design, repeated small batches let the Royal Navy build, test, operate, and refine ships before ordering them in wartime numbers. The lineage supports the description of a navy caught midway through preparation rather than surprised by the need for escorts.
Chapter · 21:20-24:46
Bittern hull lineage and iterative escort design
The Bittern, Egret, Black Swan, and Hunt lineage shows how small interwar batches accumulated the hull knowledge needed for wartime escort production.