s a requirement to keep the " aerodrome environment" visual.
I have often wondered how that is defined. If we are talking about the whole airport with associated approach lights, strobes etc then surely somewhere among that lot is a runway. But how far away from the boundary of a airport stops being "the aerodrome environment"? There may be a few local knowledge identifiable lights of a village not far from the aerodrome or a well lighted highway which skirts the aerodrome and so on. But can they truly be called the aerodrome environment? I don't know the answer. Seems to me if the visibility is so poor that you lose sight of the runway -apart from momentarily because one wing blocks your view, then maybe you should not be circling.
Navigating a circling approach based upon local knowledge street lights, villages, a moon lit river or lake or a brilliantly lit tennis court can never replace the comfort of seeing the runway on downwind and base. In addition, deliberately opting to descend below the circling MDA while on base (rather than when established in the splay on final) - and thus being entirely responsible for your own terrain clearance, will have the lawyers cheering if you crash into something while descending below the MDA.