‘Everyone knows the Alexandria in Egypt,’ writes Edmund Richardson, ‘but there were over a dozen more Alexandrias scattered across Alexander the Great’s empire.’ By the early 19th century, though, very few had been identified. Moreover, the prevailing scholarly view was that there remained ‘not a single architectural monument of the Macedonian conquests in India’ — let alone in Afghanistan, which had, ‘for more than 1,000 years… been a blank space in western knowledge’. So finding one would be ‘a world-changing achievement’.

At dawn on 4 July 1827, Private James Lewis of the East India Company’s Bengal artillery walked out of the Agra fort and into history — or at any rate into some amply trodden historical terrain. Not that he knew it. An intelligent but poor enlister from the ‘fetid’ heart of London, he’d spent six sweltering summers watching the officer class get rich, and frankly he’d had enough. ‘This is a story about following your dreams,’ says Richardson; but ‘had he known what was coming, Lewis might have stayed in bed’.

For one thing, he was now on the run, highly visible and unacquainted with the languages of India and the cholera-ridden countryside. For another, he was destitute. The only good news was that it was too hot for tigers. He emerged out of the Thar desert, at Ahmedpur (in present Pakistan), a changed man — starting with his name, which was now ‘Charles Masson’.

He was neither an especially hardy traveller nor a brilliant linguist, but he discovered two crucial things about himself: a capacity for fleshing out the bare bones of the truth (not least in order to tell people what they wanted to hear), and an increasing passion for Afghan history and the travels of Alexander the Great. In particular, he decided he would locate the Alexandria ‘beneath the mountains’: a city in the shadow of the Hindu Kush, established as a retirement/convalescent camp for Macedonian soldiers and being written about more than 1,000 years later by Chinese travellers.

He read the Greek historians on Alexander. He picked up market chatter about relics found around the Kabul area. And he began to be shown battered, indecipherable coins, bearing the likenesses of unknown kings. From this unpromising start, Masson became the first westerner in centuries to see the Buddhas of Bamiyan; he deciphered the forgotten script of Kharosthi, unearthed the priceless Bimaran casket (now a centrepiece of the British Museum), and after five years of wandering in the wilderness discovered (spoiler alert: but this is on page 2) a lost city buried beneath the plains of Bagram.

From fragments, and with next to no education or guidance, he became an archaeologist whose work, within two years of his arrival in Kabul, would be discussed in learned circles in Bombay, Bengal and London. Masson had soon ‘spent more time in Afghanistan than everyone else in Britain combined’, and much against his will, he became a spy in the service of the company he had deserted a decade earlier. Assassins came for him; he was imprisoned on charges of being a Russian agent, and, like any half-decent adventurer, he read his own obituary at least once. To his dismay, his reports were subsequently used to justify the First Anglo-Afghan War.

Richardson is a natural teller of such exuberant stories and the book is full of colourful characters: the inept and fickle Alexander Burnes, the ‘ten-cent Machiavelli’ Josiah Harlan and the Kurtz-like Lieutenant William Loveday; one-handed, mustachioed Afghan potentates, psychopathic French mercenaries and treasure-hunting, cocktail-shaking Transylvanians; chancers, lunatics, quack physicians, naked Biblical dogmatists and self-professed alchemists.

The life of Masson is, ‘despite the best efforts of almost everyone involved, a true story’, and I’ve not read anything this rollicking in years. A not unrepresentative paragraph mentions the throne of Solomon and Noah’s Ark in as many sentences; elsewhere there is a City of Screams. The fact that Masson stumbled uncomprehendingly upon the lost, 4,000-year-old Punjabi civilisation of Harappa is dispensed with in a page.

Unfortunately for Masson, he was an unfaltering trouble-magnet. His nadir came when, amid the opening salvoes of the Great Game, having been coerced into the ludicrous defence of a besieged, fleabitten town (both sides, in cahoots, were firing blanks), all ten years of his papers, books and artefacts were pillaged by a rampaging mob.

He returned to England a dejected man and tried, unsuccessfully, to sue the EIC for his losses; desk-bound ‘scholars’ stole and bowdlerised his painstaking research and the British Museum refused him a position. He died, 12 years after finally escaping the subcontinent, of ‘disease of the brain’. Not so much as a portrait of him survives.

Richardson’s is not just another ripping (if tragic) Victorian orientalist yarn, however. In 1835, the abiding western historical consensus was that the entire project of Alexandrianism had been undone by the weakening of west-east, Greek-barbarian distinctions. But Masson single-handedly compiled the first coherent evidence of an ancient Afghan civilisation where Buddhism was practised, Chinese silks traded with Rome and the ‘King of Kings’ acclaimed in Greek. These syncretic, multicultural hotspots were, Richardson argues, Alexander’s real legacy.

While Masson’s energies were fixed exclusively on finding ‘Alexandria beneath the mountains’, Richardson’s focus is more consistently on Masson’s finding (or re-creating) of himself. And if Masson — no doubt forgivably — proved incapable of wrangling his groundbreaking conclusions into book form, then Alexandriahas now done that for him — retrieving this extraordinary man from quite undeserved obscurity.