Pope Urban IV
After the death of Leone da Perego in 1257, Ottone was supported by Cardinal Ubaldini as successor to the Archdiocese of Milan, against Raimondo della Torre's candidacy. This action displeased city's lord Martino della Torre (relative of Raimondo), which claimed the historical autonomy of Milan on Archbishop's appointment. Despite Martino's opposition, Pope Urban IV chose Ottone as new Archbishop on 22 July 1262.