John of Gaunt

John of Gaunt, Duke of Lancaster (1340–1399), was the fourth son of Edward III. He married Blanche of Lancaster and became one of England's richest landowners, fighting in France and Spain.

As his elder brother the Black Prince fell ill, John assumed much of the government. Through his second wife Constance he claimed the crown of Castile, and in 1386 he arranged the Anglo-Portuguese alliance.

He wielded great influence under Richard II and mediated between the king and rebellious nobles. After his death in 1399 the crown confiscated his estates; his son Henry Bolingbroke seized the throne as Henry IV, founding the House of Lancaster.