In discussing the survival of inquisition records in the opening pages of his book, Thomas O'Connor notes, tongue in cheek, that many catastrophes befell inquisition archives in the eighteenth and early nineteenth centuries ‘because it was not a universally beloved institution’. Quite. Yet, O'Connor's painstaking research, spanning three centuries, into the largely untapped records of some five hundred Irish individuals who found themselves before the Inquisition, has succeeded in providing further insight into the complexities of an institution that has been more often caricatured than understood. These records are a veritable cornucopia, casting new light on areas as diverse as the history of Irish migrants (military, clerical and mercantile) in both Europe and the New World, conversion narratives in the early modern world (including the testimonies of Irish converts to Islam), expectations regarding religious knowledge and popular piety and, notably, the little studied area of the Irish female migrant experience and the social complexities surrounding the processing of sexual offences. Finally, as ever, the volume details the realpolitik which underpinned all diplomatic and commercial relations among powers which adhered to competing expressions of the Christian faith.

Diplomatic relations had a large bearing on the activities of the Inquisition. For instance, when Spain was at peace with England, the Inquisition was obliged to treat English vassals with more care. In fact, it often found that the Spanish government moved to frustrate many of its investigations when diplomatic issues were at play. There were also significant commercial interests to be considered. Spain and England relied on their respective trading links and as early as 1575 protective measures were put in place to ensure that visiting English, Irish and Scots Protestants were allowed to proceed with their mercantile pursuits without interference from the Inquisition. The Treaty of London in 1604 stipulated that the subjects of the king of England ‘be not molested or disturbed contrary to the rights and privileges of commerce for conscience sake, unless they have given scandal or offence to others’ (p. 29). This treaty gave Protestant migrants in Spain a degree of leeway. While not expected to attend Catholic services, they were required to observe due reverence if they did visit a Catholic church. Even with regard to the possession of so-called heretical books, this was permitted as long as the books were strictly for their own personal use.

The malleability of the Inquisition, not always a word that one naturally associates with the institution, also comes across in O'Connor's work. At a time when waves of skilled migrants were making their way to Spain, and were needed to maintain its military and naval machines, the Inquisition found itself being used as an instrument of naturalisation for the many Irish and English Protestants who were arriving on Spanish shores. In so doing, it adapted itself to the needs of state by assuming a key role in a very streamlined conversion procedure. Protestants who migrated to Spain usually appeared only once before the tribunal, giving an account of their past faith history, and petitioning to be admitted, or very often re-admitted to the Catholic Church. The would-be convert would then be absolved and his/her religious instruction entrusted to a catechist, often a fellow countryman. The vast majority of the Irish who appeared before the Inquisition were not individuals who were exposed for heresy, but Protestants (often former Catholics) who needed to re-embrace Catholicism to be admitted to the country and who approached the Inquisition of their own free will. But here, too, something significant can be said about early modern conversion. As O'Connor puts it, ‘religious conversion was less a personal or spiritual event than a practical consequence of professional life and social expectations’ (p. 3). In essence, working migrants were satisfied to do what needed to be done and the cross-confessing proclivities of the migrant Irish were well known. Indeed, the Inquisition records throw up their fair share of what O'Connor terms ‘religious weather vanes’ (p. 72). Among the most dramatic of these was the English Dominican (of partly Irish parentage), Thomas Gage, who, while assigned to the Philippine mission, got cold feet and moved to the Guatemalan mission before eventually becoming wholly discontented and returning to England where he converted to Protestantism and turned priest-catcher.

Irish Catholic immigrants to Spain often found work for themselves as interpreters who assisted with conversion procedures involving Irish or English Protestants. Irish clerics who were drawn upon to assist with catechetical instruction often found that this provided a gateway for them into Spanish ecclesiastical networks. Employment with the Spanish Inquisition was a much sought-after position for a certain kind of Irish Catholic migrant on the make, offering income, status and the prospect of further career advancement. Indeed, a large number of visiting Protestant ships found it useful to have at least one token Catholic on board for the purposes of interacting with the visiting commissioner from the Inquisition when the vessel reached Spanish shores.

O'Connor's records show that the Inquisition did not always treat equally those who appeared before it and could show a degree of leniency when it suited. The defendant Theobald Nash, a naval gunner with a Spanish wife, who had been living in San Juan de Ulúa on the Gulf Coast of Mexico, is a case in point. Brought to trial in 1604, he was denounced by several of his acquaintances for harbouring heretical views which included a dismissal of Catholic doctrine, some rather unsacramental views on marriage and a degree of libertinism regarding sex that made his associates blush. Although these accusations might have been enough to land him in serious trouble, the Inquisition, in fact, treated him lightly. Bearing in mind that he was a highly experienced gunner whose skill-set and potential contribution to colonial defences outweighed his suspected heresy, Nash got away with a prescribed penance of some religious instruction in a monastery.

Meticulously researched and beautifully written, this remarkable volume will be required reading for anyone interested in early modern history in general and migrant history in particular.