It would appear that he inherited the family estates centred on the manor of Llansadwrn in Cantref Mawr directly from his grandfather. He first appears in the records as steward of Cardigan in 1309 , and in the course of the next few years he acquired other offices of profit in south-west Wales .
It was, however, the support which he gave to the Despensers which in 1322 brought him into a position of real eminence when he was appointed deputy to the royal justice in South Wales , given leases of Dinefwr and Dryslwyn , granted the lordship of Narberth , and made sheriff of Carmarthen with custody of the town and castle. In consequence he was deeply involved in the crisis over the abdication of Edward II in 1327 , and may only have escaped complete destruction by a hasty flight to Scotland . A little later he was restored in possession of his lands, but again in 1330 he was obliged to seek asylum overseas because of his part in a premature attempt to unseat the regents. Later in the same year, when the personal power of Edward III was at last established, Rhys was recalled, was eventually restored to many important offices, and henceforth until his death played a leading role among the Welshmen of his day in furthering Edward 's foreign adventures.
In all the Scottish expeditions between 1310 and 1341 , and afterwards in the French campaigns , he figures not only as the organizer of native levies in south-west Wales , but as an active campaigner and the most prominent of the Welsh captains. He was knighted between June and Nov. 1346 , possibly after Crecy at which battle he was present. But he was not to see the second great military triumph of the reign, for he d. a few months before Poitiers , on 10 May 1356 , at Carmarthen , where he was interred, possibly in the church of S. Peter in which his grandfather was buried.
Meanwhile he had m. Joan de Somerville> , a wealthy heiress who had brought him land in as many as six English counties, which, with phenomenally extensive properties in Carmarthen and Cardigan , passed to his son, Sir RHYS THE YOUNGER (b. 1325 ). These unusually large Welsh estates for the period in which Sir Rhys flourished, and indeed the first of their kind in Wales , continued in the hands of his male descendants until the marriage towards the close of the 15th cent. of a sole remaining female descendant with Thomas ap Gruffudd ap Nicolas of Dinefwr ; the eldest son of that union was Sir Rhys ap Thomas (q.v.) . Among other interesting family connections, Sir Rhys was related to Sir Gruffydd Llwyd (q.v.) , and to the poet Dafydd ap Gwilym (a son of his maternal cousin), who has included certain references to Sir Rhys in a poem composed about 1346 . There is also a poem by Iolo Goch in Rhys 's honour.
Professor Thomas Jones Pierce, M.A., F.S.A., (1905-1964), Aberystwyth
Published date: 1959