The poison maiden - P. C. Doherty

1308: murder and mayhem are rife in the court of Edward II. The 'Poison Maiden' is rumoured to have arrived in England forcing Mathilde of Westminster to face her most dangerous opponent yet.

England hovers on the brink of civil war. Edward II, his wife Isabella and the royal favourite Gaveston, Earl of Cornwall, have been forced to retreat to the King's 'folly', as just an arrowshot away lie the Great Lords and Philip IV of France. They demand the King surrender Cornwall, so they can charge him with high treason.
Edward is trapped, and worse, he has learnt that Philip has the 'Poison Maiden' on his side, a formidable spy who did untold damage during his father's reign. As Edward tries in vain to unmask the identity of the spy, Mathilde, handmaiden to the Queen, is called upon to assistance the King in his endeavours.
Soon the crisis spills over into violence. The Lords attempt to take Cornwall by force and the King and his Court, including Mathilde, are forced to flee. As the enemy closes in, Mathilde finds herself embroiled not only in a brutal struggle for the English crown, but also for her own life.