21(2)Where a power is conferred or a duty imposed on a person requiring him to do an act or thing, then, unless a contrary intention appears, the power may be exercised and the duty shall be performed from time to time as occasion requires, and when the power is so conferred or the duty imposed upon the holder of an office as such, the power may be exercised and the duty shall be performed by the person for the time being charged with the execution of the powers and duties of the office.