Common law is a peculiarly English development. Before the Norman conquest, different rules and customs applied in different regions of the country. But after 1066 monarchs began to unite both the country and its laws using the king’s court. Justices created a common law by drawing on customs across the country and rulings by monarchs. These rules developed organically and were rarely written down. By contrast, European rulers drew on Roman law, and in particular a compilation of rules issued by the emperor Justinian in the 6th century that was rediscovered in 11th-century Italy. With the Enlightenment of the 18th century, rulers in various continental countries sought to produce comprehensive legal codes.