Henry of Grosmont, 1st Duke of Lancaster KG (c. 1310 – 23 March 1361), of Bolingbroke Castle in Lincolnshire, was a member of the English royal family and a prominent English diplomat, politician, and soldier. He was the wealthiest and most powerful peer of the realm. The son and heir of Henry, 3rd Earl of Lancaster, and Maud Chaworth, he became one of King Edward III's most trusted captains in the early phases of the Hundred Years' War and distinguished himself with victory in the Battle of Auberoche. He was a founding member and the second Knight of the Order of the Garter in 1348, and in 1351 was created Duke of Lancaster. An intelligent and reflective man, Grosmont taught himself to write and was the author of the book Livre de seyntz medicines, a highly personal devotional treatise. H