Later in 626 he inquired of Cyrus, Bishop of Phasis and metropolitan of the Lazi, whether his terminology was correct." Cyrus was uncertain, and by the emperor's order wrote to Sergius the Patriarch of Constantinople, whom Heraclius greatly trusted, for advice. Sergius in reply sent him a letter said to have been written by Mennas of Constantinople to Pope Vigilius and approved by the latter, in which several authorities were cited for one operation and one will. This letter was afterwards declared to be a forgery and was admitted to be such at the Sixth General Council."