‘Old John of Gaunt, time-honour’d Lancaster’ John of Gaunt (1340–1399) was the son of one king and the father of another. He claimed a Spanish kingdom via his wife, daughter of King Pedro the Cruel. He was the wealthiest, most powerful and most hated man in England for decades. He had a famous and enduring love affair with his mistress Katherine Swynford, whom he later married. He was sometimes the ally and sometimes the enemy of his capricious nephew Richard II. His descendants battled for control of the kingdom during the Wars of the Roses. Via his three marriages, he was the ancestor of numerous royal and noble families across Europe. John of Gaunt is the first biography of this most intriguing of men to appear for decades, and the first to tell his personal story.