One should never address an eminent person familiarly. Under even the greatest difficulties one should never do this. To you such a person are degraded by such a manner of address.
न जातु त्वमिति ब्रूयादापन्नोऽपि महत्तरम्। त्वंकारो वा वधो वेति विद्वत्सु स विशिष्यते॥