The Flower-class design was ready before the war emergency

The Second World War Flowers were not designs improvised after hostilities began. Studies stretched back to 1933, the design was standardized by the end of 1938, and the first orders were placed in July 1939. Most hulls were laid down as war began, so the emergency changed production tempo rather than creating the design. The Navy selected a commercial hull and machinery pattern capable of carrying a previously defined sensor and weapons fit. Prewar procurement had prepared commercial yards for expansion before the convoy crisis became acute.