This natural history of unicorns is not a work of dark and devious wit like A Short History of Tractors in Ukrainian; it really does trace the unicorn, in many guises, from cuneiform script through to the Hebrew Bible, Greek versions of travellers’ tales, the Septuagint, the second-century Physiologus, medieval bestiaries, religious and secular art, at last refining in the fourteenth century to the image now familiar to us, the prancing, white, fabulous palfrey with its single horn. These tangled threads resemble a page from a children’s puzzle book, a dense web where you’ll reach the end if you stick to the right line. But here you don’t really reach the end. The author promises something and it doesn’t happen. Nonetheless the journey is enjoyable and you learn a vast number of interesting and useless facts and lots of good words too – astragal, rhinocerine, alexipharmic, osteodentine (‘which has an attractive porridge-like appearance’).

The very important thing about the unicorn would appear to be its single horn. Funny, that. Or not, for after all, that’s what the Latinate word means, as does its Greek precedent, monoceros. ‘Who or what was the unicorn?’ is the central question, and the contenders are countless and crazy, with the rhino and the mighty aurochs (a giant ox) crashing into the lead, despite the fact that they bear scant resemblance to the beast as described in numerous divergent accounts. And what of the onager, the musk ox, the kiang or chiru, the atti, or the okapi? Two horns may pass for one in a profile painting. Or anywhere, if you want them to. The book is studded with fetching pictures of creatures which may or may not have combined chimerically to create the mythic beast, described in early days at greatest length by Ctesias, a Greek physician at the Persian court, in 398 BC. Its coat is white, its head dark red, and its eyes dark blue; it is swifter than all beasts, and impossible to capture alive. Its horn, crimson, black and white, confers immunity to disease and poison when carved into a drinking vessel. And so the image recurs in varied forms through antiquity, endorsed by Aristotle, Pliny the Elder, and the Septuagint translation of the Bible from Hebrew to Greek. This Biblical authority derives from the arbitrary translation of the Hebrew reem (‘large, horned, domestically useless’) as monoceros. Maybe it was the aurochs, maybe it wasn’t. But from then on, it has one horn, and is a unicorn and in the Bible, so it must be true. Furthermore, it comes to represent first the glory of God, then Christ and his union with God. ‘Who is the Unicorn, but God’s only Son?’ demanded Bishop Ambrose, one of the Latin fathers of the early Church.

Dense symbolism and allegory accrued, thanks to Tertullian and other inventive theologians, and what is hard to follow in writing was transmuted into intricate beauty by illustrations deriving first from medieval bestiaries, which would describe the animal and then recount its mystic role in the life of the spirit. So the unicorn we recognise steps into tapestry and fresco, its horn symbolising salvation and divine union; humble and lowly, it is caught for us by the Virgin Mary. Hunters will come with spears and take it to the king in his palace as God’s will took Christ back from us, and it will live again, perhaps bleeding pomegranate juice and seeds, triumphant symbols of rebirth. What sublime fusion of allegory and romance is worked into those tapestries of gardens enclosed, strewn with flowers and trees, beasts wild and gentle; what joy, what pain.

From this high point the book wanders into more digressive realms, medicinal properties, commercial products, and further improbable identifications, allowing a very dear photograph of musk oxen and a cuddly calf. Narwhals and walruses offer up their horns to the confusion of quack pharmacology. 

By the eighteenth century nature’s laws had been harshly illuminated; Aristotle and the Bible were found wanting, and unicorns lost their interest – but not for long. Romantic excitement in travel, the supernatural and the noble savage sent scholarly explorers to India and to darkest Africk. No unicorns, as usual, but Lavers tells a wonderful true story of diplomacy, a pygmy city no higher than a dining table, a taxidermist and an okapi, all set against a Congo background. This chapter is the finest in the book and could stand on its own, vivid, poignant and fraught with a dry and delicate wit.

Our times seem drab after such exploits, and there are odd lacunae – no mention of the wealth of unicorn-related art history, or the creature’s prominent place in psychology; but one mustn’t grumble. Why not instead hark back to the mighty aurochs, most ancient and favoured contender for unicornity, and consider the closing lines of Lolita, where Nabokov writes, ‘I am thinking of aurochs and angels, the secret of durable pigments, prophetic sonnets, the refuge of art. And this is the only immortality you and I may share, my Lolita.’ A twentieth-century image of the unicorn and the maiden, Humbert and his Lo? Just a thought, but not without its charms. And now, as Lavers remarks, the mythic beast seems to have become the preserve of New Age crystal keepers. In their pungent emporia one may find holograms of moonlit unicorns breasting the whelm of ocean. I bought one myself for my small granddaughter. Soon afterwards, she and I were wandering in a May-time wood; a shaft of sunlight dazzled the glade before us, and a seemly virgin led a unicorn of my own devising through bluebells and campion into the shadowed beech trees and out of sight. I recounted this heavenly incident to a Cambridge psychologist. ‘Of course you will tell her it wasn’t true,’ she said. I certainly will not. The child has seen a unicorn forever. 

Unicorns don’t exist, but we want them to exist. Why not? Thus have gods come into being. Meanwhile, in some remote hortus conclusus of the mind, the creature lingers yet, grazes and kicks up its heels. See it caracole.