What is the threshold for an interlocutory injunction?

Counsel for the parties have differing views of the threshold test for an interlocutory injunction. Counsel for the applicant relies on American Cyanamid Company v. Ethicon Limited, [1975] A.C. 396. Lord Diplock stated: The use of such expression as ‘probability’, ‘a prima facie case’, or ‘a strong prima facie case’ in the context of the exercise of a discretionary power to grant an interlocutory injunction leads to confusion as to the object sought to be achieved by this form of temporary relief. The court no doubt must be satisfied that the claim is not frivolous or vexatious; in other words, that there is a serious question to be tried ... So unless the material available to the court at the hearing of the application for an interlocutory injunction fails to disclose that the plaintiff has any real prospect of succeeding in his claim for a permanent injunction at the trial, the court should go on to consider whether the balance of convenience lies in favour of granting or refusing the interlocutory relief that is sought.