The Prince's Man. The Gareth & Gwen Medieval Mysteries, #13

Gareth & Gwen are caught up in another round of wedding mayhem in medieval Wales! In the aftermath of Prince Rhun's death, King Owain and King Madog agreed their children should marry as a way to seal the peace between them. Two years later, the wedding date has finally arrived, though relations between the two kingdoms have improved only to the extent that they aren't actually at war. So when an innocent falls victim to a poisoned dish, even Queen Cristina is so desperate for the event to take place that she begs Gareth and Gwen to head off another round of murder-and wedding mayhem-in medieval Wales. The Prince's Man is the thirteenth Gareth & Gwen Medieval Mystery. Complete Series reading order: The Good Knight, The Uninvited Guest, The Fourth Horseman, The Fallen Princess, The Unlikely Spy, The Lost Brother, The Renegade Merchant, The Unexpected Ally, The Worthy Soldier, The Favored Son, The Viking Prince, The Irish Bride, The Prince's Man, The Faithless Fool, The Honorable Traitor, The Admirable Physician, The Shattered King.
Also The Bard's Daughter (prequel novella).