[No. 40, October Term, 1943.] Decided December 15, 1943. Theatres and Shows — Licenses — Duress — License Fees Paid Under Mistake of Law. In action by operator of non-stop dance contest, known as a "walkathon," in the City of Baltimore to recover public dance license fees paid under invalid statute to secretary of Baltimore Police Commissioner, burden was upon operator to proved that the fees had been paid under duress. p. 408 Where operators of a non-stop dance contest paid to the Police Commissioner