UK common law is the foundation for all laws
It was a very simple doctrine, cause no loss or harm to others.
Stautory laws have been added since, preventative laws like speeding for example.
Under common law you could drive around past schools at 100mph and not break the law until you killed someone,
Brehon Law in Ireland said that you could pretty much kill someone if you had enough to pay the family compensation.
Rich people often did