'Y Beibl cyssegr-lan sef Yr Hen Destament, a’r Newydd’ by William Morgan, was the first whole translated version of the Bible to appear in Welsh. It took some years for the work to be completed in printed form; between the Act of Parliament of 1563 and its publication in 1588. Morgan was a Cambridge graduate and later became bishop of Llandaf and St Asaph. He based his translation on the Hebrew and Greek original Bibles, consulting also the English Bishops’ and Geneva versions. ‘Y Beibl cyssegr-lan’ included original translations as well as adaptations of Salesbury’s New Testament. No other Welsh book has been as influential for it is a work of great linguistic and literary significance. The translator skilfully moulded the classical language of the poets into the literary Welsh known to us today. In short, the book is the foundation stone on which modern Welsh literature has been based. It also allowed a highly monoglot Welsh population to read and hear the Scriptures in their own language for the very first time.