Original: Feudal royal regent The title of Lord Protector was originally used by royal princes or other nobles exercising an individual regency (i.e., not merely member of a collegial regency council) while the English monarch was still a minor or otherwise unable to rule.
Simplified: The title of Lord Protector was first used by royal princes or other nobles who ruled while the English monarch was still too young to rule or was not able to rule for some other reason.