In 1189, while Henry II was fleeing from Philip II, King of France, and his son Richard, who rebelled against his father, William Marshal, while covering the retreat of King Henry, unhorsed Richard. He could easily have killed him, but instead, killed Richard's horse. What if during that skirmish, Richard was killed by Marshal, either accidentally or not.
Who would be king of England when Henry II dies a days later? John, I presume, would be king ten years earlier. Would he have gone to the crusade in the Holy Land? How does this affect the Third Crusade, and having John king from 1189?