Variable-pitch propellers in warships

Which ship first used variable-pitch propellers?

The exchange does not establish a first ship. Early civilian examples, larger-ship adoption, and naval use are discussed separately, with several dates and ship identifications left uncertain.

No first ship is securely identified. The discussion initially places widespread adoption in larger civilian vessels around the 1960s and 1970s, then considers later European warships, including FREMM and De Zeven Provinciën. These are tentative distinctions between experiments, civilian service, and naval adoption. A viewer's recollection of a 1920 trawler at Porth Penrhyn prompts a clarification that the discussion had shifted toward larger ships and widespread use. Type 31 is identified as using controllable pitch, while Type 26's arrangement remains uncertain during the exchange. Later suggestions concerning Canadian destroyers cannot be confirmed from the notes at hand, and their absence from those notes is explicitly not treated as disproof.