Of obscure nobility, La Valette rose to prominence as a favourite of Henry III, who created him duke and peer of France in 1582. He and Anne de Joyeuse acted virtually as prime ministers in the 1580s. His rapacity was notorious, but he also showed great political ability and energy and did much to defend the crown during the civil wars of Henry's reign. Temporarily out of favour with the king, he returned to his side after the murder of Henri, Duke de Guise (1588), and advised reconciliation with Henry of Navarre, the future Henry IV of France. When Henry III was murdered (1589), Épernon at first refused to serve Henry IV, who was then still a Protestant, and even made a secret treaty with Spain. When Henry was established as king, however, Épernon appeared at court posing as a loyal subject. He joined in every conspiracy of the reign without ever being caught, and there are grounds for believing that he helped to arrange the murder of the king by François Ravaillac, who is known to have received money from Épernon's mistress, Catherine du Tillet, and who was kept in protective custody by Épernon for a whole day after the murder (May 14, 1610). Épernon then carried out the minor coup d'état that made Marie De Médicis regent for Henry's infant son Louis XIII, but she did not include him in her government. He fell into disgrace after Louis came into power (1617) but avenged himself by planning Marie de Médicis' escape from her exile in Blois in 1619 and supporting her in the civil war that ensued. In 1622 he was appointed governor of Guienne, where he lived in wanton luxury punctuated by quarrels with the archbishop of Bordeaux. Cardinal de Richelieu deprived him of his governorship in 1638 and exiled him to Loches in 1641.