English Royalty. 1st Duke of Lancaster. Born the fourth son of Edward III Plantagenet and Queen Philippa of Hainault (or Hainaut), at Ghent (or Gaunt) in Flanders. He was made Earl of Richmond in September 1342. He married Blanche, Countess of Derby in May 1359, with whom he had seven children, including the future Henry IV. After his marriage, he was styled as Earl of Derby and of Leicester. He was appointed Knight, Order of the Garter (K.G.) in April 1361. He gained the title of Duke of Lancaster in November 1362 . After the death of his wife in 1369, the ambitious Duke married Costanza, the daughter of Pedro I, King of Léon and Castilla in 1372, with whom he had two children. After his marriage, he was styled as King John of Léon and Castilla. He took Katherine Swynford as his mistress about the same time, and with her had four children, who were given the surname Beaufort. He campaigned with his elder brother, Edward of Woodstock, and took part in the conflicts of the Hundred Years War. After the death of his brother in 1376, he was in the ascendancy at court, however, favor coincided with widespread resentment of his influence among the English population. When his father died in 1377, and was succeeded by Edward's 10 year old son, John became the protector of the young king and effectively ruled England during his minority. His decisions on taxation however, culminated in the Peasants' Revolt in 1381. In 1386, he left England in an unsuccessful attempt to claim the Castilian throne. Upon his return to England in 1389, he served as mediator between the king and the Lords Appellant who had been on the brink of violence. In March 1390, Richard II invested John as Duke of Aquitaine. Costanza died at Leicester Castle in March 1394, and John married his mistress, Katherine, in 1396 at Lincoln Cathedral. The couple's children were legitimized by Richard II and the Church, but barred from inheriting the throne. He died at Leicester Castle three years later at the age of fifty-eight, he was buried beside his first wife in the choir of St Paul's Cathedral.