De principis instructione

De principis instructione, translated variously as Instruction for a Ruler or The Instruction of Princes is a medieval Latin treatise on kingship by Gerald of Wales. The first distinction takes the form of a traditional "mirror for princes", while the second and third present a narrative of Henry II's rise and fall and constitute a sustained polemic against him and the Angevin dynasty. The first distinction likely circulated c. 1191, while the complete work was likely released c. 1216×1217 during the First Barons' War when the Angevin dynasty appeared on the verge of collapse. Surviving only in a single manuscript, Cotton MS Julius B XIII, De principis instructione did not circulate widely though it was used for the Polychronicon by Ranulph Higden. Extracts were first printed in 1715, and most of the work was published in 1891 in the Rolls Series. The complete work with parallel text translation was published in 2018. Modern scholars consider it an important source for historical events of the period, including as evidence for views critical of the English monarchy at the time of the Magna Carta