Since the mid 1500s, when England became a Protestant country, there was a strong anti-Catholic feeling amongst many Protestants. English Catholics were often thought of as plotters who would conspire with Catholic countries abroad to invade and force the population to convert to Catholicism.
After the failed Gunpowder Plot of 5 November 1605, which had attempted to blow up Parliament and assassinate King James I, there were annual church services in remembrance. During these services church ministers would often preach against Catholicism and by the 1660s, effigies of the Pope and the devil were burned in the streets every 5 November.
These prejudices had a profound influence on the way Londoners reacted to the disaster of the Great Fire. It was seen by many as a deliberate Catholic plot and books and pamphlets were written afterwards proclaiming Catholic involvement in the fire.