Hew J
As you know from our dealings off forum, I'm always happy to help fellow pilots if they have a specific problem. But, just like everyone else who posts on this site, I only spend time in a discussion for as long as I find it interesting/productive/enjoyable. This thread, for me at least, no longer falls into any of those categories so I'm afraid my answer will be as brief as courtesy to you permits.
See:
ANO 2000, Article 70 'Flying Displays'
Article 129 (Interpretation)
Rule 5.
I entirely agree with the rationale behind A&C's post which started this discussion, but I draw a distinction between flying a RIAB when there is other traffic to be alarmed, inconvenienced or endangered and when there is not. The former is, at best, irresponsible (+ bad airmanship) and, at worst, illegal; the latter is, IMHO, not.
Final3G doesn't care for "this type of logic" and apparently considers it to be "semantics"; he's entitled to his opinion. If anyone had suggested ignoring a rule because it cannot be enforced, his Moulton quotation would have been relevant. No-one has suggested ignoring any rule, enforceable or otherwise.
Back to the day job ................................
[Edit]
F3G - just seen your post whilst checking how mine had come out ...
I didn't say "the manouevre isn't dangerous, the decision to do it is.", or anything like it. That would indeed be absurd semantics. My point throughout has been that there is nothing inherently dangerous in flying a RIAB - it depends upon the circumstances. Busy circuit = irresponsible, bad airmanship and possibly illegal by reason of endangering.
Empty circuit = not irresponsible, not bad airmanship, no 'endangering', not illegal.
The fatal at NW was tragic, but I see nothing whatsoever wrong with RIABs
provided the time and place allow the manoeuvre to be flown safely. I do not accept there is a problem which needs to be addressed by the imposition of a rule - either by airfield operators or by the CAA.