In 1198, King Henry II of England invaded Ireland and gave the part of it he controlled to his son John as a Lordship when John was just 10 in 1177. When John succeeded to the English throne in 1199, he remained Lord of Ireland thereby bringing the kingdom of England and the lordship of Ireland into personal union. Successive Kings of England also had the title of Lord of Ireland until the title was abolished by Henry VIII, who was made King of Ireland by the Parliament of Ireland by the Crown of Ireland Act 1542.
John, also known as John Lackland (Norman French: Johan sanz Terre), was King of England from 6 April 1199 until his death in 1216. John lost the Duchy of Normandy to King Philip II of France, resulting in the collapse of most of the Angevin Empire and contributing to the subsequent growth in power of the Capetian dynasty during the 13th century. The baronial revolt at the end of John's reign led to the sealing of Magna Carta, a document sometimes considered to be an early step in the evolution of the constitution of the United Kingdom.
The Royal style of King John was "Rex Angliae, Dominus Hiberniae, Dux Normanniae, et Dux Aquitaniae"
(King of England, Lord of Ireland, Duke of Normandy and Duke of Aquitaine).