Book of Iorwerth

The Book of Iorwerth is one of the three main groups of Welsh lawbooks, representing a significant compilation of medieval Welsh prose. While no manuscripts from the time of Hywel Dda (c. 910–950), after whom Welsh law is traditionally named, still exist, the oldest surviving lawbook is a Latin manuscript from around 1200. The Book of Iorwerth manuscripts are the oldest among the Welsh lawbooks, which date from the 13th or early 14th centuries.1

These lawbooks were created by practicing lawyers and served as instructional texts. The Book of Iorwerth, in particular, contains strata of legal provisions, some of which were already obsolete by the 13th century, while others represented living law or recent innovations. For instance, its land law section details procedures for claiming land, reflecting a transformation from a non-judicial possession method to a possessory action. The book also includes practical rules for cattle trespass and joint plowing contracts, which gained importance in the 13th century.1