This pirate lived in the 13th century and was connected to some major events in British and French history. During his lifetime he was so notorious that people would tell kids that if they were bad Eustice the Monk would come to take them away.
Research:

Behind the Scenes Minis: Bad Laws, Bad Cats
23:33

Carrington Event
43:31

United States v. Bhagat Singh Thind
46:30