Peniarth 51, also known as Llyfr Gwilym Tew ("the book of Gwilym Tew"), is a Welsh manuscript written in the second half of the 15th century. It is mostly in the hand of the bard Gwilym Tew (fl. 1460–1480). Although Gwilym Tew is known to have written other manuscripts, Peniarth 51 is the only complete manuscript that can be definitively attributed to him.
The manuscript is held at the National Library of Wales in Aberystwyth as part of the Peniarth Manuscripts collection (formerly the Hengwrt library, assembled by Robert Vaughan in the 17th century).
Contents: The texts within the manuscript include a poetic vocabulary compiled by Gwilym Tew, drawing on sources such as the Book of Aneirin (which he possessed at the time), and Bwystori Serch, his own translation of the French work Bestiaire d'Amour by Richard de Fournival. Also included are historical triads (Welsh Triads) and poetry by Dafydd ap Gwilym, Iolo Goch, and Rhys Brydydd.
Provenance: During the 16th century, the manuscript was owned by the poet and genealogist Gruffudd Hiraethog, who may have acquired it from his friend and teacher Lewys Morgannwg. The signature of the poet Roger Kyffin (c. 1587–1609) from Denbighshire also appears in the manuscript. It later became part of Robert Vaughan's Hengwrt library and subsequently the Peniarth library.
