A legal practitioner or the authorised representative, as the case may be, who has tendered advice in connection with the institution of any case or other proceeding before the Appellate Tribunal or has drawn pleadings in connection with any such matter or has during the progress of any such matter acted for a party, shall not, appear in such case or proceeding or other matter arising there from or in any matter connected therewith for any person whose interest is opposed to that of his former client, except with the prior permission of the Appellate Tribunal.