King John (r. 1199–1216) is best remembered for granting Magna Carta in June 1215, although he sought its annulment almost immediately. The youngest son of Henry II (r. 1157–1189), John succeeded his brother, Richard I who is known as Richard the Lionheart (r. 1189–1199), as King of England in 1199. His reign was marked by a string of unsuccessful military campaigns, a prolonged struggle with the Church and the baronial rebellion which led to Magna Carta.
John exploited his feudal rights to extort money from the barons: he set taxes at very high levels, he enforced arbitrary fines and he seized the barons’ estates. John used this income to fund his expensive wars in France, but still he failed to hold together the empire created by his father.
John was an efficient and able administrator, but he was also unpredictable and aggressive. He disregarded justice when dealing with opponents, regularly taking hostages and imposing ruthless punishments.
His conflict with the Church led to his excommunication. The annulment of Magna Carta by Pope Innocent III in August 1215, at John’s request, led to a renewal of the baronial revolt which was still raging when John died in October 1216.
Further information about the life of King John can be found via the Oxford Dictionary of National Biography.