On 21st of October 1966, disaster struck the village of Aberfan when 150,000 tonnes of coal waste slid down a hillside, engulfing Pantglas Junior School.
Gareth Jones, one of Mrs Williams' former pupils who was six-years-old at the time, said her "quick thinking" saved his life.
The latest series of Netflix's The Crown features the story of Aberfan and the role of former Welsh Secretary George Thomas.