As a would-be romantic novelist, I first tackled the Roman period with a “straight” historical novel (at least, as straightforward as anything by me will ever be) about the long love affair between Antonia Caenis and Vespasian. This would appear many years later as The Course of Honour, though after I had finished it I started to think only my closest friends and family would ever see it.

I needed a new direction. My research into the Rome of the Caesars was what then gave me the idea, partly as a joke of course, to set a typical private eye figure, like those of the modern genre, among the graceful porticoes and dangerous back lanes of the Golden City two thousand years ago. This seemed an exciting milieu in which shady and colourful characters could operate scams. The post-Claudian era, with the Empire just settling down into its most glorious years, offered an apparently respectable, well-run society where plenty of people would be on the make in ways that might or might not be legitimate. Just like the classic gumshoes, an “informer” (a delator) would have to be a streetwise dodger living on his wits and by his fists, despised for his chosen career.

Archaeology even allows him the right kind of upstairs tenement office; the living quarters of ancient Rome were gimcrack places which we know from the Latin satirists were dangerously neglected by crooked landlords. They consisted of cramped, teeming, repetitious apartments where the poorest lived up the most flights of stairs. To this eyrie all kinds of characters could come in the traditional manner, bringing Falco dubious offers of poorly paid work. The vigiles, the night watch who acted as both fire brigade and police force, could provide our hero with a friend in officialdom, that indispensable old pal and contact whom all successful private eyes cultivate.

At the same time, because my man would not have read the books about the modern fellows, he would not know the rules and therefore need not follow them. For instance, although Falco likes women, nobody has told him he is supposed to love them and leave them; dallying with a different gorgeous creature in every adventure and never having to face an enraged father or even to risk a paternity suit. I don’t want to spoil the story so won’t say what he does instead. The way it turned out was not even what I planned, let alone what he would have expected himself…