King John of England puts his seal to Magna Carta.

John was King of England from 1199 until his death in 1216. He lost the Duchy of Normandy and most of his other French lands to King Philip II of France, resulting in the collapse of the Angevin Empire and contributing to the subsequent growth in power of the French 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 considered a foundational milestone in English and later British constitutional history.

A seal is a device for making an impression in wax, clay, paper, or some other medium, including an embossment on paper, and is also the impression thus made. The original purpose was to authenticate a document, or to prevent interference with a package or envelope by applying a seal which had to be broken to open the container.

Magna Carta, sometimes spelled Magna Charta, is a royal charter of rights agreed to by King John of England at Runnymede, near Windsor, on 15 June 1215. First drafted by the Archbishop of Canterbury, Cardinal Stephen Langton, to make peace between the unpopular king and a group of rebel barons who demanded that the King confirm the Charter of Liberties, it promised the protection of church rights, protection for the barons from illegal imprisonment, access to swift and impartial justice, and limitations on feudal payments to the Crown, to be implemented through a council of 25 barons. Neither side stood by their commitments, and the charter was annulled by Pope Innocent III, leading to the First Barons' War.