In his excellent book The Greatest Traitor Ian Mortimer states (p.188)…’With regard to secret plots, most chronicles reflect contemporary rumour and popular opinion more closely than historical facts. To put the issue in perspective, imagine the results if several amateur historians – perhaps working in retirement homes, which monasteries sometimes were – began to write up accounts of a covert political assassination five, ten, or twenty years after the event. Imagine them trying to do the same thing in an age before literacy was common, without television, newspapers, radio or railways.’
Quite! Food for thought in a much wider context than the supposed murder of Edward II.