13(1)Where during the proceedings of a group—
(a)a member of the group ceases to be a member of the Commission, or
(b)the chairman is satisfied that a member of the group will be unable for a substantial period to perform his duties as a member of the group,
the chairman may appoint any member of the Commission to be a member of the group in his place.
(2)The chairman may also at any time appoint any member of the Commission to be an additional member of a group, whether the person so appointed was or was not a member of the Commission at the time when the group was originally selected.