Roger of Wendover,to say the least, hated King John.
Roger was a monk at about the same time John was king and John
was having a large disagreement with the church at this time (he
believed that he could choose a better replacement archbishop than
the pope and after some drama he became excommunicated) which is
probably the reason that Roger hated him. Plus there was other
stuff like raising taxes and losing wars to the french, twice.