4Where—
(a)a member becomes or ceases to be the chairman or a deputy chairman ; or
(b)a member who is also chairman of one of the corporations ceases to be chairman of that corporation,
the Secretary of State may, after consultation with the chairman of the Board in a case falling within sub-paragraph (b) of this paragraph, vary the terms of the instrument appointing the person in question to be a member so as to alter the date on which he is to vacate office as a member.