John met the rebel leaders at Runnymede, near Windsor Castle, on 15 June 1215. Langton's efforts at mediation created a charter capturing the proposed peace agreement; it was later renamed Magna Carta, or "Great Charter". The charter went beyond simply addressing specific baronial complaints, and formed a wider proposal for political reform, albeit one focusing on the rights of free men, not serfs and unfree labour. It promised the protection of church rights, protection from illegal imprisonment, access to swift justice, new taxation only with baronial consent and limitations on scutage and other feudal payments. A council of twenty-five barons would be created to monitor and ensure John's future adherence to the charter, whilst the rebel army would stand down and London would be surrendered to the king.

Answer this question, if possible (if impossible, reply "unanswerable"): A council of how many barons was created to monitor John's future adherence to the charter?
twenty-five