Task: Question Generation
Input (English): Within a few months of John's return, rebel barons in the north and east of England were organising resistance to his rule. John held a council in London in January 1215 to discuss potential reforms and sponsored discussions in Oxford between his agents and the rebels during the spring. John appears to have been playing for time until Pope Innocent III could send letters giving him explicit papal support. This was particularly important for John, as a way of pressuring the barons but also as a way of controlling Stephen Langton, the Archbishop of Canterbury. In the meantime, John began to recruit fresh mercenary forces from Poitou, although some were later sent back to avoid giving the impression that the king was escalating the conflict. John announced his intent to become a crusader, a move which gave him additional political protection under church law.
Output (English): Where did John hold a council in January 1215?