Giles W-H, the answer to your postulations is as I suggested in an earlier response. If you have a problem, fuel shortage smell of hot electrics or whatever, then you are arguably "Compelled to land." In which case flash the landing lights or nav lights and land; but expect to be met by the fire service and be ready to fill in a form or two. Otherwise you got it right in your last sentence. We all know that the real world throws up conundrums which the "book" does not answer, that's why we not only learn from the book but also ( hopefully ) from experience.