 Once a magistrate's annual term in office expired, he had to wait ten years before serving in that office again. Since this did create problems for some magistrates (in particular, consuls and praetors), these magistrates occasionally had their imperium "prorogued" (prorogare), which allowed them to retain the powers of the office as a Promagistrate. The result was that private citizens ended up with consular and praetorian imperium, without actually holding either office. Often, they used this power to act as provincial governors.
