shortly after, in april 1076, bishops and abbots of the imperial transpadine party convened at pavia under the presidency of guibert and proclaimed the excommunication of gregory vii; a messenger, bearing a caustic personal letter from henry, was dispatched with the pavian reply to the pope. in response, gregory resorted to still stronger measures with regard to guibert; he excommunicated guibert by name at the lenten synod of february 1078 and with him his main accomplice archbishop tebaldo of milan.