An interlocutory injunction is a discretionary remedy which may be granted by a judge— there is no absolute entitlement to an interlocutory injunction.

The court asks two main questions:

  1. Whether the plaintiff has made out a prima facie case, in the sense that if the evidence remains as it is there is a probability that at the trial of the action the plaintiff will be held entitled to relief (often referred to as a “serious question to be tried”).
  2. Whether the inconvenience or injury which the plaintiff would be likely to suffer if an injunction were refused outweighs or is outweighed by the injury which the defendant would suffer if an injunction were granted (often referred to as the “balance of convenience”).

In order to obtain relief the plaintiff must ordinarily give an undertaking as to damages. This is an agreement that the plaintiff will pay an amount of compensation assessed by the court to be just to any person affected by the interlocutory injunction, whether or not the person is a party.

If there is not a serious question to be tried, or the plaintiff does not give an undertaking as to damages, then an interlocutory injunction will ordinarily be refused without the court needing to consider the balance of convenience. However, where the plaintiff satisfies the court that there is a serious question to be tried and gives the undertaking as to damages, the strength of the question to be tried and the value of the undertaking then become matters to be weighed in considering the balance of convenience.

A further important factor in determining whether an interlocutory injunction should be granted is whether or not damages will be an adequate remedy for the plaintiff if the injunction is not granted. Some authorities favour this being a threshold test (ie if damages would be an adequate remedy, then an injunction will be refused); others treat the adequacy of damages as a remedy as a factor to be weighed in the balance of convenience. On either approach, whether damages will be an adequate remedy may be an important factor in considering whether or not to grant an interlocutory injunction and, in some circumstances, may be decisive.