The eight manuscripts in the Iorwerth redaction, A, B, C, D, E, G, K, and Lew, may reflect the law in Gwynedd during the reign of the two Llywelyns (Llywelyn ap Iorwerth, c.1194-1240 and Llywelyn ap Gruffudd, 1246-1282), particularly Llywelyn ap Iorwerth, and the eight manuscripts form a close group. The Iorwerth manuscripts are also the oldest in date but the most developed version of the laws. A revised version of Iorwerth is found in Col, NLW Peniarth 30, ‘Llyfr Colan’. The redaction, previously the Venedotian code, is named after Iorwerth ap Madog, the lawyer who is named as the compiler of the Test Book.
See also the list of texts.
Jenkins, D., ‘Iorwerth Ap Madog: Gŵr Cyfraith o’r Drydedd Ganrif Ar Ddeg’, National Library of Wales Journal 8 (1953), 164-170.
Jenkins, D., ‘Iorwerth ap Madog a Hywel Dda’, Lleufer 17 (1961), 17-33.
*Jenkins, D., ‘A Family of Medieval Welsh Lawyers’, in Celtic Law Papers (Brussels, 1973), 121-133.
Jones, Glanville R. J., ‘The Models for Organisation in Llyfr Iorwerth and Llyfr Cyfnerth’, Bulletin of the Board of Celtic Studies 39 (1992), 95-118.