The powerful and fearsome John Charles McQuaid was the archbishop of Dublin from 1940 to the early 1970s, and was described as the ruler of Catholic Ireland. He was obsessed with protestants, communists and "moral purity", and ran a huge spying operation on the Irish population, both at home and abroad, to keep everyone in check. In the first part of this series, Diarmaid and Catriona chart his early life, his ascent to power, and his often difficult relationship with Eamon De Valera.