This chapter considers the paths by which the Catholic Church was extended into British colonies in the nineteenth century and the relationship between the settler churches and the various competing sources of clerical personnel and influence in England, Ireland, France and Rome. Mostly, this involves explaining how Irish Catholicism came to dominate the Catholic Church throughout much of the settler British world. Some of this covers familiar territory: historians have long been aware of the role played by Paul Cullen (1803–78), first as rector of the Irish College in Rome and then in Ireland as archbishop of Armagh and subsequently of Dublin, in stamping a ‘Roman mould’ on the Catholic Church in Australia and New Zealand. Other British colonies, particularly those in North America, were more successful in defending themselves from falling entirely within the Irish orbit. However, both the Australasian case and the American counter-examples need to be set within a global context that was more extensive than the British empire. As we will see, the ethnic and political profile of colonial Catholicism depended on the interaction of three forces: the Sacred Congregation for the Propagation of the Faith (Propaganda) – the bureaucracy within the Roman Curia which appointed missionary bishops and had responsibility for the conduct of missions; the hierarchies of the resurgent Catholic Church in England and Ireland who corresponded about the supply of colonial clergy; and the Association for the Propagation of the Faith (Oeuvre de la propagation de la foi) – the missionary auxiliary which coordinated fund-raising and publicity for Catholic overseas missions.