In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

What was the barons holding in thrall at the time of the negotiations?, Context: Neither John nor the rebel barons seriously attempted to implement the peace accord. The rebel barons suspected that the proposed baronial council would be unacceptable to John and that he would challenge the legality of the charter; they packed the baronial council with their own hardliners and refused to demobilise their forces or surrender London as agreed. Despite his promises to the contrary, John appealed to Innocent for help, observing that the charter compromised the pope's rights under the 1213 agreement that had appointed him John's feudal lord. Innocent obliged; he declared the charter "not only shameful and demeaning, but illegal and unjust" and excommunicated the rebel barons. The failure of the agreement led rapidly to the First Barons' War.
London