The Basel Mission emerged in 1815 from the Deutsche Christentumgesellschaft, a society founded in the late eighteenth century which brought together various dissenting and revivalist Protestant groups in Switzerland and southern Germany. Its ethos was shaped by the doctrines of Württemberg Pietism, which stressed spiritual rebirth, individual asceticism, and stern self-examination. Troubled by the unsettling social changes generated by the industrial revolution, the mission's goal in its fields of operation in West Africa and elsewhere was the creation of self-contained rural communities of pious farmers and artisans in segregated Christian “Salems”. In 1828, it dispatched four missionaries to the Danish trading outpost of Christiansborg on the eastern Gold Coast (present-day Ghana), all of whom soon died of fever. A second party followed, the sole survivor of which was in 1835 granted permission by the Danish governor and African authorities to relocate to Akropong, the capital of the Akan kingdom of Akuapem located on a range of hills to the north of the coastal Accra plains. The station would emerge in the 1840s as the headquarters of the Basel Mission's Twi language district; meanwhile, it re-established a presence at Christiansborg and began a parallel programme of linguistic research, education, and evangelization in what became its Ga language district. The mission also began to recruit African catechists from the ranks of its young male scholars, the most talented of which were eventually ordained as pastors. One of these pioneering pastors was Theophilus Opoku (1842–1913), whose reports to Basel between 1868 and 1908 are collected in this latest volume of the British Academy's “Sources of African History” series.

Scholars have long recognized the importance of the Basel Mission's archival holdings for the study of Ghana's history and culture. Yet the archive presents considerable challenges for anglophone researchers in that most of its documentation is hand-written in old German script and far from easy to decipher. The exceptions are the reports from its African operatives, all of whom – except Opoku's cousin David Asante, who was trained in Basel and learnt German – were required to write in English. Be that as it may, Michelle Gilbert and Paul Jenkins have done a fine job in publishing for the first time a complete sequence of reports by an indigenous Gold Coast evangelist. The editors bring formidable scholarship to bear on Opoku's writings: Gilbert as an anthropologist who has been studying Akuapem since the 1970s, and Jenkins as archivist of the Basel Mission between 1972 and 2003 and a historian of the Christian encounter and its documentary and photographic record. The volume opens with an informative introduction, with Jenkins writing on the institutional structure and pietist sensibilities of the mission followed by Gilbert on the history, culture, and politics of Akuapem. Opoku's 37 yearly (and a few half-yearly) reports together with an account of an 1877 journey north to the savanna trading town of Salaga are then set out in chronological order and contextualized by comprehensive and judicious annotation. The result is an engaging text which opens a window onto the intimate dynamics of a key African missionary frontier at a time of tumultuous change.

Akuapem was ethnically diverse and politically unstable, with a Twi-speaking Akan state forged in the 1730s and headquartered at Akropong laid over the top of the area's original Guan-speaking peoples. Born in 1842 in Akropong as the paternal grandson of the late omanhene (or king) Adow Dankwa I, Theophilus Opoku was drawn to Christianity after entering a missionary household at the age of seven, subsequently enrolling in the Catechists’ Seminary and being appointed in 1868 to his first post before being ordained in 1872. For the next four decades he would serve as the pastor in charge of five congregations, all of them in Akuapem except for three years at an outstation in neighbouring Akyem Abuakwa. In that time, Akuapem was incorporated into the British crown colony of the Gold Coast; its large population of enslaved people were liberated by colonial decree; commercial expansion culminated in the emergence of cocoa as a lucrative cash crop; literate education created new aspirations and avenues for social mobility; and the gradual – if often precarious – growth of the Basel Mission's communities of converts would lay the foundations for a dramatic expansion of Christianity in the twentieth century.

Opoku's writings contain much of interest for the historian of the last of these entangled processes, although disappointingly little on the others. As the editors point out, they are characterized by significant silences. Opoku was not, of course, a disinterested “ethnographic” observer of local society: his reports include valuable observations on the realm of indigenous religious belief and practice, but that realm is consistently denigrated as superstition and “fetishism” at best or “Satanism” at worst (the editors seem anxious to downplay the missionary “diabolization” of African belief, but it is there). The role of ritual specialists (duplicitous “fetish priests”) together with the sacred nature of Akan kingship (“heathenish government”) is, moreover, often wilfully distorted by Opoku to underline the veracity of the Christian message. This denigration of indigenous culture might be said to be typical of nineteenth-century African pastors, for whom the pressure to demonstrate their evangelical credentials to European superiors in a racialized mission hierarchy created a degree of psychological dissonance. Yet I could detect nothing of the ambivalence towards – and even undisguised pride in – local belief and practice demonstrated by some of Opoku's fellow evangelists such as the Ga pastor and historian Carl Christian Reindorf. Neither did he seem to relish the adversarial cut and thrust of theological debate with local “fetish priests” as has been well documented in the Yoruba region to the east. Opoku was a tough operator and much of his reportage is confined to the suffocating world of the segregated Salems and the unending struggle to police their boundaries and to enforce the inward and outward markers of pietist rectitude. That itself tells us much about certain aspects of the Christian encounter in early colonial Africa. One criticism, to end: it is unfortunate that as a research resource the volume is marred by the lack of an index, an inexplicable oversight for a collection of primary sources – especially one in which nuggets of valuable historical data are often buried in much formulaic evangelical discourse.