First Barons' War in the context of "Magna Carta"

John (24 December 1166 – 19 October 1216) 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.

John was the youngest son of King Henry II of England and Duchess Eleanor of Aquitaine. He was nicknamed John Lackland (Norman: Jean sans Terre, lit. 'John without land') because, as a younger son, he was not expected to inherit significant lands. He became Henry's favourite child following the failed revolt of 1173–1174 by his brothers Henry the Young King, Richard, and Geoffrey against their father. John was appointed Lord of Ireland in 1177 and given lands in England and on the continent. During the reign of his brother Richard I, he unsuccessfully attempted a rebellion against Richard's royal administrators while the King was participating in the Third Crusade, but he was proclaimed king after Richard died in 1199. He came to an agreement with Philip II of France to recognise John's possession of the continental Angevin lands at the peace treaty of Le Goulet in 1200.

Philip II (21 August 1165 – 14 July 1223), also known as Philip Augustus (French: Philippe Auguste), was King of France from 1180 to 1223. His predecessors had been known as kings of the Franks (Latin: rex Francorum), but from 1190 onward, Philip became the first French monarch to style himself "King of France" (rex Francie). The son of King Louis VII and his third wife, Adela of Champagne, he was originally nicknamed 'God-given' (Dieudonné) because he was a first son and born late in his father's life. Philip was given the epithet "Augustus" by the chronicler Rigord for having extended the crown lands of France so remarkably.

After decades of conflicts with the House of Plantagenet, Philip succeeded in putting an end to the Angevin Empire by defeating a coalition of his rivals at the Battle of Bouvines in 1214. This victory would have a lasting impact on western European politics: the authority of the French king became unchallenged, while John, King of England, was forced by his barons to assent to Magna Carta and deal with a rebellion against him aided by Philip's son Louis, the First Barons' War. The military actions surrounding the Albigensian Crusade helped prepare the expansion of France southward. Philip did not participate directly in these actions, but he allowed his vassals and knights to help carry them out.

Henry III (1 October 1207 – 16 November 1272), also known as Henry of Winchester, was King of England, Lord of Ireland and Duke of Aquitaine from 1216 until his death in 1272. The son of John, King of England, and Isabella of Angoulême, Henry acceded to the throne when he was only nine in the middle of the First Barons' War. Cardinal Guala Bicchieri declared the war against the rebel barons to be a religious crusade and Henry's forces, led by William Marshal, defeated the rebels at the battles of Lincoln and Sandwich in 1217. Henry promised to abide by the Great Charter of 1225, a later version of Magna Carta (1215), which limited royal power and protected the rights of the major barons. Henry's early reign was dominated first by William Marshal, and after his death in 1219 by the magnate Hubert de Burgh, Earl of Kent. In 1230 the King attempted to reconquer the provinces of France that had once belonged to his father, but the invasion was a debacle. A revolt led by William Marshal's son Richard broke out in 1232, ending in a peace settlement negotiated by the Catholic Church.

Following the revolt, Henry ruled England personally, rather than governing through senior ministers. He travelled less than previous monarchs, investing heavily in a handful of his favourite palaces and castles. He married Eleanor of Provence, with whom he had five children. Henry was known for his piety, holding lavish religious ceremonies and giving generously to charities; the King was particularly devoted to the figure of Edward the Confessor, whom he adopted as his patron saint. He extracted huge sums of money from the Jews in England, ultimately crippling their ability to do business. As attitudes towards the Jews hardened, he later introduced the Statute of Jewry, which attempted to segregate the Jewish community from the English populace. In a fresh attempt to reclaim his family's lands in France, he invaded Poitou in 1242, leading to the disastrous Battle of Taillebourg. After this, Henry relied on diplomacy, cultivating an alliance with Frederick II, Holy Roman Emperor. Henry supported his brother Richard of Cornwall in his successful bid to become King of the Romans in 1256, but was unable to place his own son Edmund Crouchback on the throne of Sicily, despite investing large amounts of money. He planned to go on crusade to the Levant, but was prevented from doing so by rebellions in Gascony.

The Treaty of Lambeth of 1217, also known as the Treaty of Kingston to distinguish it from the Treaty of Lambeth of 1212, was a peace treaty signed by Louis of France in September 1217 ending the campaign known as the First Barons' War to uphold the claim by Louis to the throne of England. When the campaign had begun, baronial enemies of the unpopular English king John had flocked to the French banner, but after John's death in 1216, and his replacement by a regent, William Marshal, on behalf of John's young son and successor, Henry III, many had switched sides. Subsequent defeats at Lincoln in May 1217 and at Dover and Sandwich in August 1217 forced Louis to negotiate.

Information on the treaties is based on three early documents but none of these is known to have been based on an original manuscript. It is known that negotiations were spread over several locations, opening on 6 September 1217 at Staines, because the royal court was nearby at Chertsey or possibly on 5 September on an island of the Thames near Kingston. Various dates for treaties are given by the sources including: