How can HMS Royal Sovereign be described as both a Revenge-class ship and a pre-dreadnought?
Short answerThey were different namesakes: the later HMS Royal Sovereign was Revenge class, while an earlier HMS Royal Sovereign led a class commonly treated as early pre-dreadnoughts.
NotesTwo generations of battleship carried the name HMS Royal Sovereign. The later vessel belonged to the Revenge class, while the earlier ship gave its name to a class commonly treated as early pre-dreadnoughts. Reusing the name therefore does not place the two ships in the same class. Class identification distinguishes which namesake a reference concerns.