Bittern Class: The Foundation Stone of the British WWII ASW efforts - Key Ship Series 5, Episode 10

The Bittern class provided the design foundation for the Flower and Castle corvettes, Hunt escort destroyers, Egrets, and Black Swans that carried British anti-submarine warfare through the Second World War.

Building the three sloops in different yards was part of a wider Royal Navy effort to preserve the industrial skills needed for rapid wartime escort construction.

Although Enchantress was the first member of the class, her conversion to an Admiralty yacht kept the class from bearing her name and gave it a distinctive peacetime role.

The sloops' official sub-20-knot speed kept them within the London treaty definition, while comparisons with later classes raise questions about how much performance their machinery could actually yield.

HMS Stork entered service as an unarmed survey vessel, but the availability of her planned weapons allowed the Royal Navy to convert the specialized peacetime hull quickly when war began.

The Bitterns prioritized merchant and fleet-auxiliary escort, anti-aircraft defence, and anti-submarine warfare while omitting the torpedoes that would have made them look like disguised destroyers.

The Navy divided minesweeping and anti-submarine roles among different sloop groups, then used exercises and command appointments to prepare officers for another submarine campaign.

HMS Shikari gave the Royal Navy a general-purpose command in which to assess Frederic John 'Johnny' Walker before directing him through Falmouth and Stork to the modified Black Swan HMS Starling.

Bomb damage off Namsos did not immediately sink HMS Bittern; her crew abandoned a badly damaged but still floating ship before HMS Janus torpedoed her to prevent capture.

A reported oil leak and uncertainty over ammunition remaining aboard HMS Bittern show why diving and managing a sunken warship demands more caution than exploring an ordinary wreck.

Bittern's six four-inch guns were usually counted as anti-aircraft armament, but their mountings could depress enough to make them useful against small surface targets as well.

Enchantress's destruction of the Italian submarine Corallo and Stork's part in four confirmed U-boat sinkings show what the Bittern design could achieve in Atlantic and Mediterranean escort service.

The closing counterfactual asks how other powers might have reacted if Britain had used the London treaty to build about nine inexpensive, sub-20-knot, 1,200-ton sloops each year from 1930.

The First World War Flower-class sloops were true war emergency ships, while the better-known Second World War Flower-class corvettes were planned before the war as quick-build escorts.