Trevor became at once prominent in the service of Richard II , acting as his ambassador in Scotland in 1397 , and just before the king's abdication in 1399 was rewarded with high secular office in Wales . But he was one of the first to desert the ill-fated monarch, who was actually made captive in Trevor 's own diocese, and it was the bishop himself who read the sentence of deposition in full Parliament . He continued prominent as a royal emissary and spokesman during the early years of the Lancastrian regime , and as late as 1403 , long after the Glyn Dŵr revolt had started, he is found deputising in Wales for prince Henry , afterwards Henry V . But suddenly towards the end of the following year he transferred his allegiance to Glyn Dŵr .
Though the facts of his career suggest that he was a typical self-seeking churchman of his age, it is to his credit that before he adhered to the patriot cause he had protested unavailingly in Parliament against high-handed treatment of his fellow-countrymen. His diplomatic experience , moreover (the Northumberland alliance of 1405 and the crucial decisions of the Pennal Assembly in 1406 owed much to his mediation and counsel), and his legal knowledge (he was a doctor in laws ) were of the highest value to Glyn Dŵr , a fact which appears to have been recognized by the other side when, in 1409 , the bishop is associated by name with Owain as one of the king's arch-enemies. He d. on 10 or 11 April 1410 , while on a mission to Paris , and was buried there, in the infirmary chapel of the abbey of S. Victor . He had at least one admirer (as bishop of S. Asaph during the years before the rebellion) for Iolo Goch composed a highly eulogistic poem (possibly two) in his honour.
There are strong grounds for concluding that Trevor was also the author of a well-known work on heraldry — the Tractatus de Armis , as well as of its Welsh version — and that he translated the life of S. Martin ( Buchedd Sant Marthin ) into Welsh (see B.B.C.S. , iv, 3, 4; v, 1). E. J. Jones has also suggested that the authorship of several historical works of the period may be attributed to him (see Speculum , xii, 196 et seq. ; xv, 464 et seq .).
Professor Thomas Jones Pierce, M.A., F.S.A., (1905-1964), Aberystwyth
Published date: 1959