4. The Comptroller-General of Patents, Designs and Trade Marks shall have power to refuse any application for the grant of a patent for any invention relating to any article of the nature specified in Annex III of the Treaty, being an invention referred to in paragraph 6 of Annex IVA of the Treaty, or to revoke a patent for any such invention, provided that he shall not exercise that power adversely to an applicant or patentee without giving the applicant or patentee an opportunity of being heard, if the applicant or patentee so requires.