Mary Blount was regarded by at least one observer as substantially responsible for changing elite attitudes towards Roman Catholicism in Britain in the second half of the eighteenth century. This essay explores the image of Catholicism that the Duchess presented to the British elite by examining her correspondence with Thomas Pelham Holles, 1st Duke of Newcastle; the chapels and interiors of Norfolk House, London, and Worksop Manor, Nottinghamshire; and her own designs for the sculpted pediments of the Manor’s façade. It will be shown that the Duchess offered, through her practices of hospitality and cultural production, a disarmingly attractive and sophisticated cosmopolitanism, alongside repeated demonstrations of loyalty to the Hanoverians. Together these belied Popish stereotypes. As an example, the Duchess’s story suggests that there was significant potential for Catholic women to exercise considerable cultural influence in eighteenth-century Britain.