GWILYM AP GRUFFYDD AND THE RISE OF THE PENRHYN ESTATE TO students of the history of late-medieval Wales, Gwilym ap Gruffydd ap Gwilym is now a familiar figure. He is credited with laying the foundations of the first substantial estate in Gwynedd to be built up by purchase and the family which he founded was to dominate the principality of north Wales until the Union. It was the late Glyn Roberts who first drew attention to Gwilym's significance and it was one of his pupils, the late John Rowland Jones, who solved the mystery of his connection with Gwilym ap Gruffydd ap Tudur of Llaniestyn near Beaumaris, who died in 1376 and, in his will, left the lands he had acquired in Anglesey and Caernarfonshire in tir prid to Gwilym's father. He also cleared up the inconsistencies and anachronisms in the traditional account of the origins of the Penrhyn family. J. R. Jones's thesis has often been cited and quoted; it is certainly one of the significant contributions to the study of north Wales in the later middle ages and of those leaders of the native community who formed the Welsh political nation after 1282 and whose dominance continued after 1536. Glyn Roberts and J. R. Jones based their work on the rich collection of Penrhyn deeds and family papers deposited in the Library of the University College of North Wales in 1939. In 1983 this collection was augmented by a further deposit from Penrhyn Castle, the existence of which was previously unknown; it included a large quantity of medieval documents relating to Anglesey and Caernarfonshire.2 In these circumstances it seemed appropriate to look again at the beginnings of the Penrhyn estate and at Gwilym ap Gruffydd himself, building on the work of J. R. Jones. Like so many landed estates, Penrhyn began with a marriage. In about 1340 Gwilym's grandfather, Gwilym ap Heilin ap Gruffydd ap Tudur ab Ednyfed Fychan, married Efa, the daughter of Gruffydd ap Tudur ap Madog ab larddur. The origins of both families lay in service to the native princes in the thirteenth century; Tudur ab Ednyfed Fychan was Llywelyn ap Gruffydd's seneschal from 1268 to 1278, and Tudur ap Madog served both Glyn Roberts, 'Wyrion Eden' in idem, Aspects of Welsh History (Cardiff, 1969), pp. 206-14; idem, 'Teulu Penmynydd', ibid., pp. 254-58; idem, in Dictionary of Welsh Biography, pp. 1123-24; J. R. Jones, 'The development of the Penrhyn estate to 1431' (unpublished M.A. thesis. University of Wales, 1955). 2 1 am particularly indebted to my colleague Tomos Roberts, archivist of U.C.N.W., for access to this collection and for much advice and fruitful discussion while this paper was in preparation.