Book 14 in the Border Knight series by Griff Hosker.

King Henry is not a good king. His son, The Lord Edward, promises strength but the Earl of Leicester, Simon de Montfort seeks the throne and the crown. When civil war erupts there is only one place for the knights of the valley, now led by the Warlord's heir, Sir Henry Samuel, and that is by the side of the king. For good or ill they will do as they have always done and support the king. Their fate is entwined with the Plantagenets.