In late 1670 or early 1671, a worried father wrote to his daughter expressing concerns about rumours that she might convert to catholicism. Deeply moved, he urged her to consider the damage this would do to her and her family's reputation, stressed that catholics were disloyal to the monarchy, and offered a series of arguments against Rome being the only church in which salvation might be obtained. He coupled this with a letter to his son-in-law, pressing him to dissuade any such conversion. These letters may have been written without sight of his daughter's narrative justifying her conversion; indeed, it is possible that they arrived after she died in spring 1671. They remind us that conversion was a profound and often traumatic experience for more than just the individual convert, affecting their kin, household, and parish. Furthermore, this was no ordinary family. The father was the exiled earl of Clarendon, formerly Charles II's leading adviser; the daughter, Anne Stuart (née Hyde), Duchess of York, wife of the heir presumptive to the throne -the future catholic King James II.The conversion of the duke of York, an anonymous author wrote in 1681, was 'one of the greatest Calamities that has happened in our Age'. 1 If the numbers of converts to catholicism were fewer than anxious protestants imagined (under 2000 in the years 1669-71, by one estimate), the prominence and activism of many of these converts terrified the English protestant imagination. 2 The reign of Charles II saw the gradual exposure of catholics at the heart of government: the heir to the throne, the king's mistresses, the king himself, and some of his leading counsellors, such as Thomas Clifford. Arlington himself joined this group in