On a casual vacancy occurring in the office of chairman of any council . . ., an election to fill the vacancy shall be held not later than the next ordinary meeting of the council held after the date on which the vacancy occurs, or if that meeting is held within fourteen days after that date, then not later than the next following ordinary meeting of the council, and shall be conducted in the same manner as an ordinary election.
. . . , a meeting of the council for the election may be convened by the proper officer of the authority.
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In a parish not having a separate parish council, a casual vacancy in the office of chairman of the parish meeting shall be filled by the parish meeting, and a parish meeting shall be convened for the purpose of filling the vacancy forthwith.