duumviri
...that it was common for the Roman Emperor to be elected to one of two offices of the highest judicial magistrates known as duumviri, and the other position was left up to the emperor for the appointment of a praefectus?
...that it was common for the <a class="mw-redirect" href="./Roman_Emperor" id="mwBs4" rel="mw:WikiLink" title="Roman Emperor">Roman Emperor</a> to be elected to one of two offices of the highest judicial magistrates known as <b id="mwBs8"><a href="./Duumviri" id="mwBtA" rel="mw:WikiLink" title="Duumviri">duumviri</a></b>, and the other position was left up to the emperor for the appointment of a <a href="./Prefect" id="mwBtE" rel="mw:WikiLink" title="Prefect">praefectus</a>?