Why a Black Swan was a sloop, not a frigate

Although vessels such as Sutlej were reclassified as frigates in the 1950s, that change in terminology says little about their original design. The comparison separates corvettes built to merchant-hull standards, frigates built partly to those standards, and fully capable convoy-escort sloops built as warships. In this interpretation, political and public language favoured the more prestigious-sounding frigate label, reinforced by the large number of wartime frigates still in service. The Black Swan remains the peak pre-war anti-submarine sloop within this design lineage. Its ancestry and construction standard matter more than the category applied to it later.