Surveying the British Empire at its peak, Geraldine Vaughan examines “Ultra-Protestant” individuals and organizations who campaigned across Britain, Canada, and Australia – in print, on speaking tours – to defend the Empire's traditional Protestant British supremacy just as it became more tolerant and diverse than ever before. These struggles involved people of primarily European descent in regions where they made up the vast majority of the population. All confronted a growing Roman Catholic population. Most of those Catholics were Irish in origin, but Canada also had French descendants of the old colony of New France who had been incorporated into the Empire on the eve of the American Revolution. There too, though, Irish Catholic immigrants made up an increasingly significant portion of the population, just as they did in northwest England, western Scotland, and the various provinces of Australia that also form the geographic focus of this book.

Indeed, Ireland's challenge to the Empire's Protestant hegemony looms over this anti-Catholic movement. With increasingly horror these Ultra-Protestants, who claimed to represent nothing more than the traditional values of Reformed Protestantism, watched as the Empire became increasingly tolerant of the Irish and less militantly Protestant overall. During the debates over Home Rule that began in the 1880s, Imperialists openly contemplated letting the Irish govern themselves. Then, during World War I, Irish nationalists launched an armed struggle for independence that eventually led to the partition of the island into a still British north and an Irish Republican south in 1921. By then, to be “Irish” implied being Roman Catholic, and being Irish Catholic was fundamentally associated with poverty, ignorance, idolatry, superstition, and various other typical tropes of anti-Catholic ideology that had been circulating since the Reformation (the book's first chapter provides a usefully up-to-date survey of the historiography of anti-Catholicism in the modern British world). The many Protestants of Irish descent cherished their British identity, one they believed to be fundamentally Protestant. For these anti-Catholics, to be Protestant in a Protestant-dominated empire gave one the benefits of economic prosperity, civil and political liberty, and intellectual freedom, in addition to righteous religion.

To both commemorate the triumph of Protestantism following the Glorious Revolution of the 1688 and keep Roman Catholics (especially the Irish ones) subordinate, militant Irish Protestants had been organized since the late eighteenth century into the trans-national Orange Order. Although the Orange Order and other early anti-Catholic figures appear in Vaughan's book, her focus is on the series of new anti-Catholic societies that began to form in the 1880s. They organized the Imperial Protestant Federation (IPF) in the 1890s to reinvigorate the faltering struggle against Roman Catholic influence within the Empire. This book's second chapter surveys this expanding alliance and its mobilization to preserve Protestant hegemony in an Empire that seemed perversely intent on relinquishing it. Realizing they could not completely turn back the clock, their primary goal was to prevent things from getting worse.

The IPF organized campaigns waged to uphold old anti-Catholic laws that remained on the books but were only loosely enforced. They strove to elect firmly Protestant lawmakers who would oppose the increasing strength and influence of Roman Catholic individuals and organizations across the Empire. However, Vaughan's principal concern is with the IPF's rhetoric and ideas. Her primary source material, culled from research in England, Ireland, Scotland, Australia, and Canada, is the publications (books, pamphlets, and newspapers) generated by members of the IPF. Circulated around the Empire, they were used to stiffen the spine of Protestants and inspire resistance of various sorts.

Vaughan breaks down the distinct strains of anti-Catholicism she found in these writings over the course of three chapters (the third, fourth, and fifth). Building on the work of John Wolffe, the leading scholar of anti-Catholicism in the modern British world, she boils down his four categories of anti-Catholicism (constitutional–national, theological, social–cultural, and popular) into three: constitutional, theologico-political, and socio-national. The first involves legislation, access to the political system, and governmental policies. Education, for example, was a major area of conflict, with Ultra-Protestants favoring a “secular” system that nonetheless taught basic Christian values and favored Protestant interpretations of issues like the history of Ireland. The second opposed Roman Catholic doctrine and practice as well as the allegedly tyrannical powers of Catholic priests and the Pope over the Catholic laity. Here opposition to the religion is difficult to separate from opposition to its political influence, hence “theologico-political” anti-Catholicism. Its tropes and concerns go back to the dawn of the Reformation although here, as everywhere else, Vaughan insists that anti-Catholicism adapted to changing circumstances over the centuries. Finally, socio-national is perhaps the most modern version. It drew on racist stereotypes to distinguish Anglo-Saxon Protestants from Irish and French Catholics through generalizations about national character. Here the link between anti-Catholicism and nationalism that is highlighted through the book emerges most clearly.

More than just inveterately prejudiced people, these Ultra-Protestants were responding to two major transformations in the Empire's religious life. First was increased Roman Catholic assertiveness as priests and the papacy sought to strengthen their religion and even win over new converts. Second was the growing fondness for “ritualism” within the established Protestant Church. This was a two-front war where anti-Catholicism had to fight against fellow Protestants being seduced toward Catholicism as well as actual Catholics. As Vaughan herself admits, at times it can be difficult to keep all of these concerns neatly categorized.

In the end, Vaughan sees this anti-Catholic movement as more a symptom of the age than an effective force for change. Its rearguard defense of the anti-Catholic values on which the Empire had been founded ultimately failed. However, there were unexpected results. In the final chapter, “The Twilight of Anti-Catholicism?” Vaughan explores how the IPF's arguments contributed to the secularization of the British world after World War II. Overall, her analysis provides a valuable link between early modern and present-day anti-Catholicism in the British world, even if it tells us more about what anti-Catholicism was than what it did.