Complex sentence: Much of John's later, negative reputation was established by two chroniclers writing after the king's death, Roger of Wendover and Matthew Paris, the latter claiming that John attempted conversion to Islam, a story which is considered to be untrue by modern historians.
Split into simpler sentences: Much of John's later, negative reputation was established by two chroniclers writing after the king's death, Roger of Wendover and Matthew Paris. The latter of whom claimed that John attempted conversion to Islam, a story which is held as false propaganda by modern historians.