The decision of Charles II to pursue ‘Catholic’ policies in the 1670s and the revelation of the conversion to Catholicism of his brother and heir to the throne, James, duke of York, ensured that anti-Catholicism became once again a powerful force in English politics. In this chapter it will be argued that anti-Catholicism ensured that the attempts of Charles’s chief minister in the early 1670s, Danby, to gain support for the crown failed and (more dramatically) it brought about the biggest threat to the monarchy since the mid-century: the Popish Plot and the Exclusion Crisis