 Entering the service of Eberhard, prince-bishop of Liège, he was sent by that prelate on a mission to Rome, where Pope Leo X retained him, giving him (1519) the office of librarian of the Vatican.In the following year he went to Germany to be present as papal nuncio at the coronation of Emperor Charles V, and was also present at the Diet of Worms, where he headed the opposition to Martin Luther, advocating the most extreme measures to repress the doctrines of the reformer.His conduct evoked the fiercest denunciations of Luther, but it also displeased more moderate men, especially Erasmus.