In ''Beacon Theatres v. Westover'', the Court held that a district court erred in trying all issues itself in an action in which the plaintiff sought a declaratory judgment and an injunction barring the defendant from instituting an antitrust action against it, and the defendant had filed a counterclaim alleging violation of the antitrust laws and asking for treble damages. It did not matter, the Court ruled, that the equitable claims had been filed first and the law counterclaims involved allegations common to the equitable claims. Subsequent jury trial of these issues would probably be precluded by collateral estoppel, hence "only under the most imperative circumstances which in view of the flexible procedures of the Federal Rules we cannot now anticipate, can the right to a jury trial of legal issues be lost through prior determination of equitable claims."