R Geraint Gruffydd: Scholar of the Reformation in Wales who became one of the leading figures of Welsh academic and cultural life

He wrote lucidly on William Morgan, translator of the Bible into Welsh and put together an attractively illustrated account of Welsh literature

Members of the staff at Aberystwyth University in the 1970s; Gruffydd is on the far right (Aberystwyth Uni versity Archives)

Geraint Gruffydd held some of the most prestigious posts in Welsh academic and cultural life, not least the Chair of Welsh at Aberystwyth and that of National Librarian. In 1985 he was appointed Director of the University of Wales Centre for Advanced Welsh and Celtic Studies, a post from which he retired in 1993. His most important contribution to Welsh scholarship was his work on the prose written during the Protestant Reformation and on the early Puritans.

Born in 1928 at Tal-y-bont in Merioneth, the son of a well-to-do farmer, Moses Griffith, who was the first treasurer of Plaid Cymru and friend of the party's founder Saunders Lewis, Gruffydd was educated at village schools and then went up to the University College of North Wales, Bangor, and in 1948 on to Jesus College, Oxford, of which he became an Honorary Fellow in 1992. While at Oxford, he became acquainted with Sheldon Vanauken, the American author, a friend of CS Lewis, who mentioned him in his book A Severe Mercy (1977).

His first job was that of Assistant Editor with Geiriadur Prifysgol Cymru/A Dictionary of the Welsh Language, organised on historical principles like the OED but also serving as a monolingual Welsh as well as a bilingual Welsh-English dictionary. Launched in 1921, it is a huge project still ongoing under the auspices of the University of Wales.

He stayed for only two years before his appointment to a lectureship in Welsh at Bangor in 1955, a promotion which was to set the course of his subsequent career. He moved to Aberystwyth in 1970 as Professor of Welsh Language and Literature, soon establishing himself as a scholar and critic in his chosen field. Ten years later he became Librarian at the National Library of Wales, his genial personality and high standards winning him the respect of his staff and all who used that centre of learning.

Besides many articles on the major figures of the late Renaissance and Reformation in Wales, in particular the early humanists who placed an emphasis on God's sovereign grace, justification by faith alone, the priesthood of all believers and the authority of God's Word, Gruffydd also wrote about Dafydd ap Gwilym, generally regarded as the greatest Welsh poet of the medieval period, and on Aneirin, one of the poets who flourished in "the Old North" (what are today parts of northern England and southern Scotland) in the 6th century.

He was general editor of the series Beirdd y Tywysogion ("Poets of the Princes", seven volumes, 1991-96), a field in which he was renowned for his encyclopaedic knowledge and meticulous scholarship, and he contributed to Beirdd yr Uchelwyr ("Poets of the gentry") on the poets Meilyr Brydydd, Llywelyn Fardd, Dafydd Benfras and Bleddyn Fardd.

His interests extended to early Welsh printers, the subject of his inaugural lecture at Aberystwyth, subsequently published as Argraffwyr Cyntaf Cymru ("The first printers in Wales", 1972) and to the prose writings of his father's old friend Saunders Lewis, whose literary essays he edited under the title Meistri'r Canrifoedd ("The centuries' masters", 1973). Despite his critical approach to the Roman Catholicism of Saunders Lewis, he was one of the trustees of the memorial fund established in the writer's name. He also edited a Festschrift for JE Caerwyn Williams, his predecessor at the Centre for Advanced Welsh and Celtic Studies, and was for many years an Associate Editor of the Oxford Dictionary of National Biography.

To the compendium A Guide to Welsh Literature c. 1530-1700 (1997), which he edited, he contributed an exemplary chapter on Anglican prose of the period. Among his lesser works were a study of Daniel Owen, the first great Welsh novelist, and a discussion of Gruffudd ab yr Ynad Coch's powerful elegy for Llywelyn II, the last Prince of independent Wales, killed by Anglo-Norman forces at Cilmeri in 1282. He also wrote lucidly on William Morgan, translator of the Bible into Welsh (The Henry Lewis Memorial Lecture, 1989) and the same year put together an attractively illustrated account of Welsh literature.

The range and quality of Geraint's writing were reflected in the volume Beirdd a Thywysogion ("Poets and princes", ed. Morfydd E Owen and Brynley F Roberts), a collection of essays presented to him in 1996. His own essays on literary and religious subjects, many of which first appeared in Y Cylchgrawn Efengylaidd ("The evangelical magazine"), were collected in Y Ffordd Gadarn ("The steadfast road", 2008). He was a staunch Calvinist and a leading light in the Evangelical wing of that Connexion, bringing to his fundamentalist faith a keen intelligence that he allowed to play over a wide field of disciplines. With the late R Tudur Jones, he was the foremost scholar of the Reformation in Wales and a literary critic of rare distinction.

It was inevitable that such a well-equipped scholar should be asked to serve on the myriad committees by which the cultural life of Wales is run. These included the Welsh Academy, the Welsh Books Council, the University of Wales Press Board, the Board of Celtic Studies, the Court of the University College of Wales, Aberystwyth, of which he was Vice-President, the Honourable Society of Cymmrodorion, and the International Congress of Celtic Studies, which he served as President. He was elected Fellow of the British Academy in 1991.

Robert Geraint Gruffydd, scholar and literary critic: born Tal-y-bont, Merioneth 9 June 1928; Lecturer in Welsh, University College of North Wales, Bangor (1955-70); Professor of Welsh, University College of Wales, Aberystwyth, and Emeritus (1970-80); Librarian, National Library of Wales (1980-85); Director, University of Wales Centre for Advanced Welsh and Celtic Studies (1985-93); Fellow of the British Academy 1991; married 1953 Eluned Roberts (one daughter, two sons); died 24 March 2015.