In the eighteenth century, Catholics had been systematically persecuted, for example being denied the right to inherit property. The most severe penalties were abolished in 1778, but it was only in 1829 that they were allowed to sit in Parliament, or join the army.

By 1851 just under 4% of all attendances in England and Wales were at Roman Catholic churches. This may seem surprising, but the census followed too soon after the mass Irish immigration triggered by the Potato Famine of the late 1840s for many of the new arrivals to show up as church-goers. The main concentrations were in the north west, where the Irish immigrants had just arrived. However, significant groups were found in other parts of the country, overwhelmingly in towns and in London. We cannot distinguish recent Irish immigrants from long-established Catholic congregations in these data, but there were one or two Catholic congregations in most districts, unlike the non-Conformist sects who were often completely absent away from their core area.