Circling minima is there for a reason. The prohibition on circling at night is there for a reason. It’s one thing to cancel IFR in good viz and ceiling, at a sensible circuit height, but to do a “visual” circuit when the cloud base and possibly viz are below circling minima? And IF an aircraft were flying level at 400ft over a built up area this is illegal. Obviously this is all in response to the unconfirmed speculation from other posts at this point, so these are general comments only. As always we need to wait for the official report to see what learning can be taken from this accident.