The patrimony of Tudur ab Ednyfed Fychan undoubtedly lay in the Four Cantrefs, and record evidence supports the testimony of the pedigrees that his descendants, in the line whence came the families of Griffith of Penrhyn and Williams of Cochwillan, were settled at Nant, in Englefield, and Llangynhafal, in the vale of Clwyd. So far from being settled at Penrhyn early in the 14th cent., the ‘Griffith’ family continued to live in north-east Wales until the close of the century; but three marriage alliances during the century brought them substantial property in Caernarvonshire and Anglesey.
His wife's uncles (Rhys, Gwilym, and Maredudd ap Tudur) gave full support to their cousin, Owain Glyndŵr (q.v., and see under Ednyfed Fychan); Gwilym himself was more cautious, but he was forced by family and other circumstances to throw in his lot with the rebels about 1402. (As has been said, his father and uncle died in Glyndŵr's service.) His brother, Robin of Cochwillan, was also in rebellion but abandoned Glyndŵr before 1408, when he appears as a crown official in Caernarvonshire. Gwilym also made his peace with the king before Nov. 1407, when he was restored to his forfeited possessions and was granted, in addition, the lands of twenty-seven Anglesey adherents of Glyndŵr who had probably died in rebellion. By 1410 he had been granted the forfeited lands of his wife's uncles, Rhys and Gwilym ap Tudur, both of whom adhered to Glyndŵr to the last. His will, dated 1430, also refers to lands which he had obtained from his Tudor kinsmen; his brother-in-law, Tudur ap Goronwy, appears to have d. c. 1400 and his share of the Tudor possessions undoubtedly came into Gwilym's hands. In all, Gwilym ap Griffith appears to have succeeded, through his father's marriage, his own, and the effects of the Glyndŵr rebellion, in gaining control of most of the patrimony of the Tudors; not the least important of the probable consequences was the departure of Owain Tudor (q.v.) to seek his fortunes at the court of Henry V.
The date of death of Gwilym's first wife is not known. Some time after 1405 he m. Joan, daughter of Sir William Stanley of Hooton, Ches., thus beginning a long and profitable connexion with the rising star of that family. His son by his first wife inherited only his mother's property at Penmynydd, and he was the ancestor of the later Theodores of that place (see Tudor family, of Penmynydd). Gwilym ap Griffith d. in 1431, leaving his great possessions in Anglesey and Caernarvonshire to his son by the second marriage. (Penrhyn manuscripts, passim; Trans. Angl. Antiq. Soc., 1951, 34-72; J. R. Jones, ‘The development of the Penrhyn estate to 1431’, University of Wales M.A. thesis, unpublished.)
From 1431 to 1531 the son, grandson, and great-grandson of Gwilym ap Griffith (each named Gwilym) held the estate and added to it. (During the 15th cent. the surname ‘Griffith’ became established and ‘Gwilym’ became ‘William’ in non-Welsh records.) All three showed outstanding skill in steering a safe and profitable course through the dangerous waters of 15th cent. politics; in particular, they allied themselves with prominent English houses, especially the pliant Stanleys — a process which began with the marriage of Gwilym ap Griffith to Joan Stanley of Hooton. The son of that marriage, GWILYM FYCHAN (c. 1420-1483), was under the tutelage of his Stanley kinsmen until he came of age (Penrhyn MSS. 17-18). In 1440 he received letters of denization, freeing him from the operation of the penal laws passed against Welshmen during the Glyndŵr revolt, on condition that he did not marry a Welsh-woman or hold office; the ban on holding office was raised in 1443 on the ground that his mother was a Stanley (Cal. Pat. Rolls, 1436-41 (416), 1441-6 (164). He m., before 1447, Ales, daughter and heiress of Sir Richard Dalton of Apthorp, Northants.; the marriage almost certainly reflects the Stanley connection, for Ales Dalton was grand-daughter by her second marriage of Isabel de Pilkington whose daughter by Thomas de Lathom, her first husband, brought Lathom and Knowsley to the Stanleys. (Dwnn, Visitations, ii, 155; Penrhyn MSS. 1-4, 7-9, 13; G.E.C., Complete Peerage, iv, 205 n. c.; D.N.B., liv., 75.) He m. (2) Gwenllian, daughter of Iorwerth ap David; ROBERT, his eldest son by this marriage, was the ancestor of the family of Griffith of Plasnewydd, Anglesey, and Llanfairis-gaer, Caerns.; EDMUND, the second son, founded the estate of Carreg-lwyd, Anglesey. See Griffith, Pedigrees, 47, 56, 57, and articles Griffith of Carreg-lwyd and Griffith, George, 1601-1666. In 1451 he was member of a commission appointed to examine the reasons why the revenues of Merioneth were in arrear (Cal. Pat. Rolls, 1446-52, 480) and between 1457 and 1463 he was deputy to various chamberlains of North Wales (Davies, Conway and Menai Ferries, 47; P.R.O. Min. Acc., 1154/3, 1180/3). He does not appear to have held the office of chamberlain. He was probably the William Griffith who, as ‘marshall of the King's Hall,’ received grants from Edward IV in 1462 and 1464, and he served on a number of North Wales commissions during Edward's reign (Cal. Pat. Rolls, 1461-7 (117, 293, 329), 1467-77 (54, 490), 1476-85 (121)). He was d. by 13 Sept. 1483 (Penrhyn MSS. 38-9). A number of contemporary poets (qq.v.) sang his praises — Cynwrig ap Dafydd Goch, Dafydd ab Edmwnd, Guto'r Glyn, Rhys Goch Eryri, and Robin Ddu (Mostyn MSS. 148, 493, 495, 498, 542; Llanst. MSS. 118, 78; Gwaith Dafydd ab Edmwnd (ed. T. Roberts), 107; Gwaith Guto'r Glyn (ed. J. Ll. Williams and I. Williams), 52, 55; Iolo Goch ac Eraill (ed. H. Lewis, T. Roberts and I. Williams), 307; H. T. Evans, Wales and the Wars of the Roses, 14).
He appears to have m., as his second wife, Elizabeth Grey, grand-daughter of Reginald, 3rd baron Grey of Ruthin (the enemy of Owain Glyndŵr) and first cousin to John Grey, lord Ferrers of Groby (1432-1461) who was the first husband of Elizabeth Woodville, later queen of Edward IV. (D.N.B., xxiii, 193, 197; Williams, Observations on the Snowdon Mountains, 1802, 174.) The marriage must have brought him into personal contact with the powerful Greys and Woodvilles and it would explain the presence of a William Griffith as member of Edward IV's council on 8 Aug. 1482. (Gairdner, op. cit., 338-9.)
Under Henry VII he continued to hold the chamberlainship of North Wales until 1490 when he was replaced by Sir Richard Pole (Davies, Conway and Menai Ferries, 48, 68.) He was knighted when Arthur was created prince of Wales in 1489 and he continued to serve on a number of North Wales commissions. (Cal. Pat. Rolls, 1485-94, 86, 354.) He d. 1505/6. (Penrhyn MSS. 44-5.) Among poets (qq.v.) who sang to him are Tudur Penllyn, Dafydd Pennant, Dafydd Llwyd ap Llywelyn, Lewis Môn, and Tudur Aled. (Mostyn MSS. 148, 467, 504, 532, 535; Gwaith Tudur Aled, ed. T. Gwynn Jones, i, 142.)
Professor Glyn Roberts, M.A., (1904-1962), Bangor