The qualification to stand for election is that one must have served as a City sheriff and be a current alderman. Since 1385, prior service as sheriff has been mandatory for election to the lord mayoralty. Two sheriffs are selected annually by Common Hall, which meets on Midsummer's Day for this purpose. By an ordinance of 1435, the lord mayor must be chosen from amongst the aldermen of the City of London. Those on the electoral roll of each of the City's 25 wards select one alderman, who formerly held office for life or until resignation. Now each alderman must submit for re-election at least once in every six years.