Where any heir of entail called to the succession of an entailed estate by any tailzie dated prior to the first day of August one thousand eight hundred and forty-eight shall previous to the passing of the said recited Act have granted any bond of annuity or other deed disponing or bearing to dispone, or containing obligation to dispone, such estate or any portion thereof in security, such heir of entail shall not be entitled to give consent to any application under the said recited Act or this Act which shall be opposed by any creditor in such bond of annuity or other deed as aforesaid, and who shall either hold infeftment in such entailed estate, duly recorded, or shall enter appearance and prove his debt or claim in the course of the proceedings under such application: Provided always, that it shall be competent to the Court, if, with reference to any offer of adequate security, or otherwise in the circumstances, it shall deem the opposition on the part of such creditor to be unreasonable, to disallow the same, and to give effect to the consent of such heir.