Provided always, that when a tenant in tail of lands under a settlement shall have already created or shall hereafter create in such lands, or any of them, a voidable estate in favour of a purchaser for valuable consideration, and shall afterwards under this Act, by any assurance other than a lease not requiring inrolment, make a disposition of the lands in which such voidable estate shall be created, or any of them, such disposition, whatever its object may be, and whatever may be the extent of the estate intended to be thereby created, shall, if made by the tenant in tail with the consent of the protector (if any) of the settlement, or by the tenant in tail alone, if there shall be no such protector, have the effect of confirming such voidable estate in the lands thereby disposed of to its full extent as against all persons except those whose rights are saved by this Act; but if at the time of making the disposition there shall be a protector of the settlement, and such protector shall not consent to the disposition, and the tenant in tail shall not without such consent be capable under this Act of confirming the voidable estate to its full extent, then and in such case such disposition shall have the effect of confirming such voidable estate so far as such tenant in tail would then be capable under this Act of confirming the same without such consent: Provided always, that if such disposition shall be made to a purchaser for valuable consideration, who shall not have express notice of the voidable estate, then and in such case the voidable estate shall not be confirmed as against such purchaser and the persons claiming under him.