The Long Shadow by Cynthia Harrod-Eagles

This is the sixth in Miss Harrod-Eagles Dynasty series and continues the story of Annunciata Morland at the Court of King Charles the Second. Annunciata is now wealthy and well-connected both as Countess of Chelmsford and the unacknowledged illigitimate daughter of Prince Rupert of the Rhine, uncle to the King. The death of King Charles, however, leads to civil turbulance made all the more pitiless and determined as it is based on religion. The Protestant fanatic, the Earl of Shaftesbury, uses an incendiary preacher, Titus Oates, to stir up the London mob and make accusations of sympathy for Catholicism against anyone at Court friendly towards the Duke of York later James the Second. Annunciata needs all her wits and experience to save herself and her familly from disaster. OK so the Dynasty series are supposed to be "womens books" but I like them. So there!