All business shall be considered at a meeting of the Committee, Advisory Committee or the Board, as the case may be, and shall be decided by a majority of votes of the members present and voting. In the event of an equality of votes the Chairman shall have a casting vote:
Provided that the Chairman may, if he thinks fit, direct that any matter shall be decided by the circulation of necessary papers and by securing written opinion of the members:
Provided further that no decision on any matter under the preceding proviso shall be taken, unless supported by not less than a two-thirds majority of the members.