The Catholic Church was the largest body of followers of Christianity.
As late as the early 20th century, the Church kept many books which they deemed heretical in the secret Library of St John the Beheaded in London. (PROSE: All-Consuming Fire) One of the books suppressed by the Church was the Necronomicon. (PROSE: The Banquo Legacy)
In the 16th century, many Christians split from the Catholic Church to become Protestants. Some Catholic rulers persecuted them, such as Mary I of England with the Heresy Laws in the 1550s and Catherine de Medici of France with the St Bartholomew's Day massacre on 24 August 1572. (AUDIO: The Marian Conspiracy, TV: The Massacre of St Bartholomew's Eve)
At the time of the Reformation King Henry VIII declared himself as the head of the English church. His daughter Elizabeth I later persecuted priests and followers of the Catholic Church. However the Catholics built secret rooms and passages in their houses so that the priests could hold their services in secret and escape. That was why the St Agnes Abbey also had some secret passages. (PROSE: Eye of the Gorgon)
Charles II died in 1685 and was succeeded his younger brother James II. Given that James II was a Catholic, his accession to the throne of Protestant England created discontent among the English nobility and public, which ultimately led to him being overthrown in the Glorious Revolution in November 1688. (AUDIO: The Glorious Revolution)
In July 1936, the Spanish Civil War began when a group of conservative generals revolted against the democratic government out of fear that traditional Catholic values were being undermined and the government was leaning towards Communism. (AUDIO: Fiesta of the Damned)
Sir Toby Kinsella, a senior British civil servant with the Ministry of Defence in the 1960s, was Catholic. (AUDIO: Artificial Intelligence, The Fifth Citadel) The same was true of the Seventh Doctor's companions Hex (AUDIO: Gods and Monsters) and Sally Morgan (AUDIO: Signs and Wonders) and the 2000s Deputy Prime Minister Meena Cartwright. (AUDIO: The Longest Night)
The Fourth Doctor believed the official papal seat for the Church was in the Betelgeuse system in the 33rd century. A renegade branch, known as the Catholic Church Apostolic, controlled Europa during this time. (PROSE: Managra)