Following the seizure of London by the rebel barons in May 1215, prolonged negotiations between the rival parties led to the production of a draft settlement known as the Articles of the Barons. This was probably written down at Runnymede, a few days before 15 June. Here, the points agreed between King John and his barons were arranged in two main sections. The first is divided into 48 paragraphs (marked with breaks in the left-hand margin), setting out the individual clauses which the barons had sought and the King had conceded. This ends by insisting that the customs and liberties granted by the King should be granted in turn to all landowners, thus extending the terms of the charter from the barons to the whole kingdom. The paragraph would subsequently become clause 60 of Magna Carta.

The second section records a security clause, with 25 unnamed barons acting as guarantors. This is our first evidence for the emergence of the baronial committee of 25, and it is followed by a provision for the Archbishop of Canterbury and his fellow bishops to issue their own charters, to support the 25 in preventing the King from seeking papal annulment of the settlement. The clauses are arranged in an order close to that of Magna Carta. At the bottom, the King’s Great Seal was attached as proof of his assent.

It was from this jumble of provisions that the royal Chancery prepared the final settlement, known as Magna Carta, although with several significant changes to phrasing and order. The Articles of the Barons survives because the document was taken from the field of Runnymede, almost certainly by Archbishop Stephen Langton (1150–1228), and preserved in the archiepiscopal archive at Lambeth Palace. Looted in the 1640s, it eventually found its way to the British Library.