In the 17th century, the Uffizi offered its visitors a rather more diverse range of exhibits than it does now, among them weapons made by some distant precursor of Q Branch. The Scottish traveller James Fraser on a visit to Florence in the 1650s recorded what he saw: ‘A rarity, five pistol barrels joined together to be put in your hat, which is discharged at once as you salute your enemy & bid him farewell … another pistol with eighteen barrels in it to be shot desperately and scatter through a room as you enter.’

It is not possible to go very far in the divided Europe of the early modern period without coming across some instance of the many kinds of covert activity that are chronicled in this genial and immensely readable work. The spirit of the age is captured in an extraordinary line in the poem ‘Character of an Ambassador’ by the Dutch polymath and diplomat Constantijn Huygens, which says that ambassadors are ‘honourable spies’. An unexpected page in Nadine Akkerman and Pete Langman’s book is devoted to invisible inks in the family papers of a Lancashire Catholic squire. The authors also turn their attention to the texts and objects that left Fotheringhay Castle covertly, despite the best efforts of the jailers of Mary, Queen of Scots. One such, a miniature gold and enamel triptych, is the pride of my college’s collection (you can see it in the Ashmolean Museum in Oxford, where it is on loan). The noblewoman Anne Vaux, who smuggled it out of the castle, features in Spycraft as the victim of an audacious and perfectly executed sting by the lieutenant of the Tower of London, where her friend Henry Garnett, a Jesuit priest, was imprisoned. They corresponded in invisible inks on papers wrapped round a (hint!) pair of spectacles or pieces of ‘bisket bread’, little realising that all their communications were being intercepted, the invisible inks being made legible and every letter (including seals, handwriting and invisible messages) being replaced by a counterfeit made by the master forger Arthur Gregory. 

The authors naturally examine the fight to the death between Mary and Elizabeth I’s spymaster Francis Walsingham, ‘one of the most famous cipher-driven episodes in history’. The first round of their bout, involving the incriminating ‘casket letters’, was already in the past. The final struggle drew in Walsingham’s double agent Gilbert Gifford (who made sure that his master saw Mary’s letters before her ally the French ambassador did), Walsingham’s decipherer Thomas Phelippes, and Mary’s cipher secretaries Gilbert Curle and Claude Nau. Phelippes, thanks to an earlier search of the queen’s rooms, had the cipher key in his possession. He had only to decipher Mary’s letters at top speed and bide his time. On the packet containing the final incriminating letter he drew a gallows to indicate the likely fate of his rival cryptographers. 

We are shown the letter within a letter of the valiant Brilliana Harley, in which secret statements can be picked out from an apparently innocuous communication by placing a grid over it. There is a fascinating consideration of ‘letterlocking’ – the use of anti-interception devices: triangles of paper threaded through the folded pages; slivers of paper cut from a letter’s folded edge woven through small cuts in the leaves. We are shown prodigious works of miniature writing and of writing on cloth hidden in clothing to elude searches. We are given a concise survey of disguise and introduced to one of the strangest impostures of the period – the completely bogus ‘ambassador’ from the court of King James who toured Europe on forged credentials in 1604 until he was apprehended by the wary Calvinists of Heidelberg.

The survey encompasses the darkest art of the dangerous trade of spycraft: assassination. The authors introduce us to the short pistol or ‘dag’ (the deluxe version is a pistol concealed in a book of devotions) before considering what was apparently the least precise of the dark arts: poisoning. The widely credited antidotes of the day – bezoars and narwhal tusks – of course did nothing. Poisoning generally seems to have been a less than scientific enterprise, there being no sense that the poisonous compound in some preparations was fugitive or capable of being destroyed by heat (many toads and spiders died in vain). I think, pace our ingenious authors, that we can now acquit the Caroline virtuoso Sir Kenelm Digby of poisoning his wife, as his recipe for viper wine does not include among the ingredients the venomous parts of the snake. Sadly, many equally innocent individuals accused of poisoning were not acquitted.

The work comes, as they say, with many special features, all of which demonstrate the wit as well as the learning of the authors. There is a map of the London ‘netherworld’, accurately charting prisons, residences and lodgings of individuals known to have been involved in the dangerous trade, as well as locations of letter drops, apothecaries who sold toxic substances and the courts where practitioners would end up if their enemies (or colleagues) didn’t get them first. As well as an index of names and places and an index of things (which makes for excellent reading in its own right), there is an index occultus of aliases and codenames. Yet more, there is an appendix providing practical lessons in Renaissance spycraft – instructions on counterfeiting seals, on creating ciphers and codes, on the use of cipher wheels, on handling invisible inks (do not mix up your revealing solutions!) – as well as references to video resources for folding and ‘locking’ letters. With an emphatic caution not to try any of this at home, there is a section on poisons, with a note on those substances once erroneously believed to be antidotes. Let this book be a warning: do not give aqua fortis to the cat; do not be beastly to toads in an attempt to extract their venom.

The deeper history that Spycraft traces is the way in which intelligence services run at first on an ad hoc basis, with bought-in agents, forgers, poisoners and cryptographers (and thus heavily dependent on citizen denunciations, double agents and sheer luck), developed into integrated counterintelligence units with continuities in knowledge and their own records. This is not to say that some of the freelance operatives in the earlier period were not skilled, ruthless and effective. But their knowledge and specialist skills tended to die with them, and networks usually broke up on the death (or fall from favour) of a magnate or spymaster.

Just outside the date range of this book, which ends with the restoration of Charles II, lie the two great game-changing developments in spycraft. One is the emergence of the intelligence unit or cabinet noir, an office of government devoted to the gathering and collation of information, often through the interception and decoding of letters sent via the postal system. The second is the growth of a form of encodement that went beyond even a sophisticated substitution cipher. This landmark of cryptography, apparently devised by the Jesuit polymath Athanasius Kircher as part of a peace initiative whereby princes could communicate with each other securely, reduced all languages to one language by matching key Latin words and phrases to a numerically coded lexicon. This allowed a message to be decoded in any one of five languages. Here, in embryonic form, are the elements of a modern code system and the first small steps on the path that has brought us to the device on which I type this review.

Spycraft is an excellent book, accessibly written, profoundly researched, cleverly illustrated and immensely readable. It has in it the ingredients of a wonderful documentary series illustrating the techniques through which early modern individuals via diverse deceptions attempted to shape the course of history.