Quick question on passing off/unfair competition

IPKat team member Jeremy has been pondering on something.

In all his long years he doesn't remember ever seeing a reported decision in which an English court has been asked to make a declaration that an applicant's actual or proposed activities do NOT constitute an act of passing off, in a situation in which no passing off action has been threatened or is impending. Is this because it can't be done, or because no-one has ever done it? In jurisdictions in which unfair competition principles apply instead of passing off, are things any different?

If you either know, or think you know, the answer, can you please let him know? Answers will be posted on this blog.