A person may be appointed as a member of the Authority for a designated area under the said paragraph 1(a) whether or not he is a member of the council or one of the councils by whom he is so appointed; but no person who is for the time being a member, officer or servant of the Executive for that designated area or who is for the time being a servant of a subsidiary of that Executive shall be appointed as a member of the Authority, and any person appointed to be a member of the Authority who subsequently becomes a member, officer or servant of that Executive or a servant of such a subsidiary shall forthwith vacate his membership of the Authority.