In what I suppose must be (alas) her last major work, Judith Herrin turns to a subject that combines most of the wide interests manifest in the string of books and articles that have studded her distinguished career. She first caught the attention of what is in fact a much wider world than most academics reach in her The formation of Christendom, published nearly thirty-five years ago (1987). Her subject was, in some ways, quite traditional, recalling (to mention only great works) Christopher Dawson's The making of Europe (London 1932) and R. W. Southern's The making of the Middle Ages (London 1953), both concerned with the creation of medieval Christian Europe. Herrin's approach differed from these in one fundamental way, for though both Dawson and Southern were aware that the route to the Middle Ages was deeply affected by the rise of Islam and the continuation in the East of an empire that called itself ‘Roman’, it was Western Latin Christendom to which their books led, and which they sought to explain and understand. In contrast, the final part of Herrin's book bore the title, ‘The three heirs of Rome’ – namely, the East Roman Empire with its capital in Constantinople, the Islamic Empire with its capital, from ad 750, in Baghdad (after a brief sojourn in Damascus) and the Christian Empire in the Latin West, in which Rome sought to preserve some sense of being the capital. Three heirs: there was not one route out of classical antiquity, via what had come to be called when Herrin was writing ‘late antiquity’ – there were three, and which, if any, was the ‘true’ heir was by no means clear; scholarship over the last half-century has not made it any easier to decide, if indeed it is worth deciding.

Judith Herrin thereafter became well known as a distinguished Byzantinist, publishing Women in purple: rulers in medieval Byzantium (London 2001), Byzantium: the surprising life of a medieval empire (London 2007) – both books aimed beyond the world of academe – and then in 2013 two books of collected papers, Unrivalled influence: women and empire in Byzantium, and Margins and metropolis: authority across the Byzantine Empire. The very titles of these books reveal two things about Herrin's interests as a Byzantinist: first, an interest in the place of women in the Byzantine world – mostly noble, if not imperial, women, something determined by the nature of the sources, but none the less easily overlooked (or patronised) before Herrin's research; and secondly, an attempt to get behind the importance traditionally attached to the Byzantine capital, Constantinople – traditionally, not only in the sense of traditional scholarship but also, less easy to escape, embedded in many of the sources available to the Byzantinist, written either in the capital or from the point of view of the Byzantine court, whether imperial or patriarchal. Another feature of Herrin's scholarship – found across her works, though on display in her papers – is her gift as a miniaturist, focusing on some particular text, or image, or person, or object or means of trade – coins, for example – and illuminating the wider picture by concentration on minute particulars. My favourite among her miniatures is her wonderfully detailed walk through Byzantine mathematics, inspired by Andrew Wiles's solution to Fermat's last theorem (‘Mathematical mysteries in Byzantium: the transmission of Fermat's last theorem’, Margins and metropolis, 312–34).

Looking back over Herrin's career like this, one might think that she was destined to write her latest book on Ravenna. It could be regarded as playing to her strengths as a miniaturist, Ravenna itself being the minute particular (one chapter, ‘The anonymous cosmographer of Ravenna’, especially displays such skills). That, however, is only a beginning, for, in Herrin's hands, Ravenna is seen to serve several themes dear to her heart. Art, for a start: Herrin's several discussions of the magnificent mosaics that still miraculously survive do not so much illustrate, as provide real insight into, themes such as the relationship between the Arian Christianity inherited by the Visigoths and the Catholic Christianity of the imperial court; the way in which imperial power is presented and wedded to the whole rich symbolism of the Christian Church; and the place of the feminine – witness the procession of women martyrs in S. Apollinare Nuovo, and the Empress Theodora and her entourage facing her husband and his entourage, not to mention Galla Placidia, the first imperial woman to make her home in Ravenna, who built there her mausoleum. Politics, which can be presented as Herrin does, in terms of tension between the margins and the metropolis, with Ravenna moving from the margins to occupy the centre as the Visigothic capital and later the seat of the Roman exarchate in the West, provoking a struggle with Rome with its claim to be the centre, with Ravenna then receding to the margins as its authority declined and was finally extinguished by the Lombard conquest of northern Italy – and then, finally, the role Ravenna played in Charlemagne's assumption of political ascendancy in the West, as emperor of the Romans, so that Herrin can claim for Ravenna the final distinction as ‘Crucible of Europe’.

Holding the focus on Ravenna seems from time to time to be something of an effort, mostly because when Ravenna is at the margins, by definition the action is really somewhere else, but also because, even when Ravenna is at the centre, the sources on which Herrin has to rely are meagre in the results they yield. Another way in which Herrin attempts to move beyond the traditional imperial and political story is, in some of the chapters, to conclude with some reflection on what it was like to live in Ravenna in the period just covered; it is a noble endeavour, certainly worth the attempt, but sometimes defeated by recalcitrant evidence.

The book is beautifully produced, with plates that do more than illustrate, as Herrin makes them yield genuine insights. It is a worthy tribute to a distinguished career.