CPC- sec 11 Munni Bibi v. Trilokinath, 58 IA 158, 165, where it has been said that to apply the rule of res judicata as between co-defendants three conditions are requisite. "(1) There must be a conflict of interest between the defendants concerned; (2) it must be necessary to decide this conflict in order to give the plaintiff the relief he claims; and (3) the question between the defendants must have been finally decided."