Notwithstanding anything to the contrary in this Act contained, the master of a ship, a container operator or the pilot of an aircraft, instead of himself performing any act, including the answering of questions required by or under any provision of this Act to be performed by him, may at his own risk, appoint an agent to perform any such act, and any such act performed by such agent shall in all respects and for all purposes be deemed to be the act of the master, container operator or pilot, as the case may be: Provided that the personal attendance of the master or pilot may be demanded by the Controller.