Was it not reviewed by 3 seperate judges ? An appeal was denied because it would have been a waste of time. Depp didn't have a case.
Permission to appeal is reviewed by a single judge at the Court of Appeal. It is only heard by three judges if there is a hearing. Lord Justice Underhill refused permission on the basis of there being no real prospect of success and there was no compelling reason for the appeal to be heard.
The "real prospect of success" is a prospect of succeeding in establishing one's case at trial, a task which is more onerous for the claimant.
Essentially the Court of Appeal judge deciding on a PTA, looking at the trial judge's ruling, will first determine whether the trial judge has made any errors of law, and then consider whether the judge's conclusions were reasonable ones to make.
The compelling reason relates to whether there is a compelling question of law that would benefit from an appellate decision, which clearly was not an issue in this case.