And to the intent that the inheritance of such part of the hereditary revenue of the Crown arising in and by the General Post Office which is vested in His Majesty may be preserved in the Crown for the future benefit thereof, be it enacted and declared that the same or any part thereof shall not hereafter be alienable, chargeable, or grantable, by His Majesty, his heirs or successors, for any estate, term, or time whatsoever to endure longer than the life of His Majesty, or of such king or queen as shall make the alienation, charge, or grant, and that all gifts, grants, alienations, and assurances whatsoever to be had or made of, and charges upon, the said duties or revenue, or any part thereof, contrary to the provisions of this Act, shall be null and void without any inquisition, scire facias, or other proceeding to determine, or make void the same.