Reverend John Williams (1811-62), also known by his bardic name of Ab Ithel, graduated from Jesus College, Oxford, in 1835. Williams was an important member of the 'old literary clerics', a group of nineteenth-century clergymen who promoted Welsh language and culture. Published by the Rolls Series in 1860, this work was largely inspired by such patriotic sentiment. Presented here in the original Latin, this edition is a collation of three linked manuscripts. The first is the oldest surviving copy of the chronicle and ranges from 444 to 954, where it is continued by two later manuscripts until 1288. Information has also been taken from other authorities, such as the Anglo-Saxon Chronicle and Florence of Worcester, when the same events have been recorded. Incorporating elements of hagiography, these annals document the reigns of kings and the Norman Conquest. They remain a unique and valuable record of Welsh history.