@flying lawyer.
I don't know what actually happens in terms of enforcement of rules. Clearly if there is a complaint by the public this is investigated and as a pilot I am most certainly not advocating more of that of course.
What I do wonder is how enforcement of the rules is made outside of a complaint by the public or an accident. The AAIB have done a great job in a short time in this incident. Should there be similar random reviews of flights in known poor weather or is that just impractical/too costly? In this example would Heathrow Radar have reported the transgression into r157 or their concern about the weather during that flight "accept VFR if you can"?
Accepting earlier comments on the impracticalities of analysing localised weather and providing a commercial service in these sorts of variable conditions.
Apologies if this is ground that has been covered many times before.