Being an American and not knowing about the Aberfan disaster, I had to do a bit of research after this episode, and hoo boy... It was just as bleak and difficult and gut-wrenching as this show made it out to be.
The image of the schoolteacher, looking out the window at the sludge approaching, will probably haunt my dreams soon. He went from a rather cool-mannered character ("don't peak early", he tells his singing student dryly) to screaming at the kids to take cover.
That last scene, from the terse conversation with the PM to crying over the hymn, is why I adore Olivia Colman. It