Approach to an interim prohibitory injunction (American Cyanamid principles)

In American Cyanamid Co v Ethicon Ltd [1975] UKHL 1, Lord Diplock rejected any requirement to show a prima facie case on the balance of probabilities. The court must first be satisfied that the claim is not frivolous or vexatious, in other words that there is a serious question to be tried, and it should not try to resolve conflicts of evidence on the written material. If there is, the court considers whether damages would adequately compensate the claimant if it wins at trial and the defendant could pay them. If not, it considers whether the defendant would be adequately protected by the claimant's undertaking in damages if the defendant wins. Where doubt remains, the court weighs the balance of convenience, and where other factors are evenly balanced it is prudent to preserve the status quo. Greystone has not yet launched, which may favour restraint. Unless the court orders otherwise, an interim injunction order must contain the applicant's undertaking to pay any damages the respondent sustains which the court considers the applicant should pay (CPR 25.9(3)(a)).

Why A is wrong: American Cyanamid rejected a requirement to show a probability of success; a serious question to be tried is enough at the first stage.

Why B is wrong: The court should not try to resolve conflicts of evidence at the interim stage; that is for trial.

Why D is wrong: Inadequacy of damages for the claimant is only one stage; the court must also consider the defendant's protection and the balance of convenience.

Why E is wrong: CPR 25.1(1)(a) lists an interim injunction as an interim remedy that may be granted before trial.