art of war and, in this, he conformed to the medieval notion of good kingship. As a warrior he was so successful that one modern military historian has described him as the greatest general in English history. He seems to have been unusually devoted to his wife, Queen Philippa. Much has been made of Edward's sexual licentiousness, but there is no evidence of any infidelity on his part before Alice Perrers became his lover, and by that time the queen was already terminally ill. This devotion extended to the rest of the family as well; in contrast to so many of his predecessors, Edward never experienced opposition from any of his five adult sons. Issue Sons Edward the Black Prince (1330–1376), eldest son and heir apparent, born at Woodstock Palace, Oxfordshire. He predeceased his father, having in 1361 married his cousin Joan, Countess of Kent, by whom he had issue: King RichardII. William of Hatfield (1337–1337), second son, born at Hatfield, South Yorkshire, died shortly after birth and was buried in York Minster. Lionel of Antwerp, 1st Duke of Clarence (1338–1368), third son (second surviving son), born at Antwerp in the Duchy of Brabant, where his father was based during his negotiations with Jacob van Artevelde. In 1352 he married firstly Elizabeth de Burgh, 4th Countess of Ulster, without male issue, but his female issue was the senior royal ancestor of the Yorkist King EdwardIV: Philippa, 5th Countess of Ulster. Descent from Lionel was the basis of the Yorkist claim to the throne, not direct paternal descent from the 1st Duke of York, a more junior line. Secondly, in 1368, Lionel married Violante Visconti, without issue. John of Gaunt, 1st Duke of Lancaster (1340–1399), fourth son (third surviving son), born at "Gaunt" (Ghent) in the County of Flanders, which city was an important buyer of English wool, then the foundation of English prosperity. In 1359, he married firstly his distant cousin the great heiress Blanche of Lancaster, descended from the 1st Earl of Lancaster, a younger son of King HenryIII. By Blanche he had issue: Henry of Bolingbroke, who became King HenryIV, having seized the throne from his first cousin King RichardII. In 1371, he married secondly the Infanta Constance of Castile, by whom he had issue. In 1396, he married thirdly his mistress Katherine Swynford, by whom he had illegitimate issue, later legitimised as the House of Beaufort. His