When Commodore became a substantive Royal Navy rank

Was Commodore historically a temporary appointment rather than a permanent Royal Navy rank?

Yes for much of the late twentieth century, when it was often tied to a post; it later became a substantive one-star rank.

Earlier Royal Navy officers could hold Commodore for a particular job and later revert to captain, without any guarantee of promotion to rear admiral. Michael Clapp's Falklands-era career illustrates that older pattern. A commodore appointment could therefore signal a role without permanently changing the officer's substantive grade. The rank was later made substantive to remove ambiguity and align the Royal Navy more closely with allied one-star structures.