Although it's since emerged - and been even longer suspected - that a disaster of its magnitude could've been averted, most of those to whom blame has been apportioned over the intervening half century, are now dead ... and, as Tuesday night's documentary presented by the BBC's Huw Edwards revealed, there're still numerous questions that remain unanswered. Moreover, many of those seem unlikely ever to be ... despite the massive changes to the surrounding landscape ... brought about by subsequent clearances of the slag heaps!