Medieval England knew two forms of divorce. The first, and overwhelmingly the most important, was divorce a vinculo matrimonii (from the bond of marriage), a ruling by the Church that a marriage had never been valid. This turned on some default in the couple’s consent to it, either that consent had been coerced or they themselves were canonically incapable of giving it (because, for example, they were underage or too closely related to make a valid marriage). The second, what might be termed a separation, was divorce a mensa et thoro (from bed and board), a ruling that the couple need no longer live together on the grounds, most commonly, of cruelty or adultery. TheHistoryOfParliament.com
