10.—(1) If the Mayor is a member of the Metropolitan Police Authority, he is to be chairman.
(2) If the Mayor is not a member of the Metropolitan Police Authority he shall before each annual meeting appoint a chairman from among its members.
(3) On a casual vacancy occurring in the office of chairman, an appointment to fill the vacancy shall be made by the Mayor —
(a)before the next meeting of the Metropolitan Police Authority (other than an extraordinary meeting), or
(b)if that meeting is held within fourteen days after the date on which the vacancy occurs and is not an annual meeting, not later than the next following meeting.