In May 1215, a group of discontented barons renounced their fealty to King John and rebelled, naming Robert Fitzwalter (d. 1235) as their leader. Self-styled as ‘Marshal of the Army of God’, Fitzwalter was lord of Little Dunmow in Essex, holder of Castle Baynard within the City of London, blood-related to the Earls of Clare, Winchester and Hereford – and what’s more, he had a history of resistance to the King. He had even been implicated in a plot to kill him. He was, therefore, well-placed to lead the rebellion and bring unity to the group.
In return for their extensive landholdings, the barons owed military service to the king, their overlord, although they often paid a levy called ‘scutage’ in place of undertaking direct military action. The barons also owed the king payments relating to their estates. In the time of King John, these were set at extortionate levels, so many barons decided to join the rebellion in 1215.
Under Fitzwalter’s leadership, the rebel barons captured London on 17 May 1215, and the following month finally forced King John to grant Magna Carta. The barons then made peace with the King and renewed their allegiance to him. Magna Carta also contained a clause which provided that 25 barons should oversee the enforcement of its provisions. However, just over two months after it was first granted, Magna Carta was annulled by Pope Innocent III, and it was not long before the barons were again at war with King John.
Further information about the life of Robert Fitzwalter can be found via the Oxford Dictionary of National Biography.