Mariano F. Urresti (Santander) has a degree in History and is the author of almost twenty books on historical enigmas, including Los templarios y la palabra perdida, La vida secreta de Jesús de Nazaret and Felipe II y el secreto de El Escorial. Among other awards, he won the III Premio Finis Terrae de Ensayo Histórico for his work La España expulsada. Las violetas del Círculo Sherlock is his first novel.