Why the Royal Navy built Castle-class corvettes

Castle-class corvettes continued the corvette line after the Flowers, even as the Royal Navy introduced larger frigates. Yards unable to build frigates could take Castle contracts. The class is also interpreted as insurance against putting too much reliance on the River frigate design. Producing several escort types spread the risk of an unsuccessful design or an unsuitable production route. Destroyers, destroyer escorts, frigates, corvettes, and trawlers all contributed to the escort force. Comparing navies only by destroyer totals therefore misses much of the Royal Navy's smaller-vessel capacity.