The Follies of the King by Jean Plaidy

This book is the eighth volume in the Plantagenet Saga, and the action takes place in the reign of Edward the Second, and charts the events precipitated by Edward’s attachments to and preference for handsome young men. His queen the beautiful Isabella was not to forgive or forget her humiliation. The country was in turmoil. Robert the Bruce had beaten the English at Bannockburn. The King was making deadly enemies throughout the country, but did not realise that the most deadly of these was the Queen. Alluring, powerful, and ruthless, she waited until she took a lover Roger de Mortimer, and together they worked to overthrow the man who had humiliated her. While Edward plunges along the road on which his follies had set him, and which ends with the most horrific murder in history.