I am on the fence as to whether illegal IMC with a test candidate is a good or bad thing (from a training point of view).
Apart from the legal issues, putting your trust in the only AI on board, which when new costs about £2500 (in aviation most things are expensive I consider this quite cheap and they do wander off more than I like) may not be overly sensible.
However I know a lot of pilots who have had this experience with examiners far more experienced than me and it taught all of them the same lesson.
I think that some people like JJs quoted examiner are MORE than capable of handling themselves in situations likes this but that is a whole different discussion I think and one on which I am not necessarily qualified to comment on. My concern would be if the experience taught the exam candidate that IMC was ok because he handled it on the day (with an examiner ready to take over from him if it went wrong, thus lowering the perceived pressure on him).
I've went IIMC for 30 odd seconds (pre my IR) towards a hill, made a 180 degree turn and GOT AWAY WITH IT several years ago and scared myself shi1tless and vowed never to do it again.
After the fact I wished someone had done it to me to teach me a lesson.
If we all operated within the rules GENERALLY we would be ok, but the one thing newly qualified or inexperienced pilots lack is an ability to assess while in the air whether what they are doing is legal, questionable or stupid / illegal.
My view while on the ground at the planning stage the flight should be legal then safe, in the air flying it should be safe then legal (they are not always the same thing, and as JJ points out no one has ever flown into the ANO).
Sorry if I am going off on one, but I've been preparing the safety presentation for Redhill since 0630 this morning and this seems relevant.
Cheers
Gary