Bad, bad King John - the treacherous brother who tried to take his brother King Richard's throne while he was away fighting during the Crusades. John is something of a pantomime villain these days and his popular image as a selfish, cruel, tyrannical, violent man is largely true, although he was well-read and a capable administrator. But did he personally murder his errant nephew Arthur of Brittany to prevent him from succeeding to the throne of England. It's a great story, shocking if true - but is it?