October 21, 1966, the day when 116 children and 28 adults died in Aberfan, South Wales, after rain-soaked coal waste slipped down a mountain engulfing a school, marks one of the most harrowing events in Queen Elizabeth’s reign.

The Aberfan disaster was always going to be a key storyline in season three of The Crown – as writer Peter Morgan strove to tell the tale of one of peacetime’s darkest days though the eyes of the local people, the Queen and senior royal family members.