"Double Jeopardy" has been an accepted rule in Britain (England anyway) since "time immemorial" i.e. the accession of Richard I (Lionheart). However, the binding legal precedent which finally established this wasn't made until 1830-something, if I recall; also, the same ruling did away with the right of a hulking defendant to challenge his accuser (the frail father of a raped and murdered daughter) to mortal combat.

I'll try and look up the name of the case.