When in Rome

After the success of Emperor: The Gates of Rome, it is quite likely that Conn Iggulden's second instalment of the life story of Julius Caesar, published today, will do just as well. Emperor: The Death of Kings (HarperCollins), however, leaves him well short of his conquest of Gaul, and I would guess that Iggulden is embarked on an epic series that may run to five or six books.

I didn't read Iggulden's first novel and for a good reason. Intermittently over the past 20 years I've been engaged in writing a series of novels about the last years of the Roman Republic and the first century of empire. There are now six of them and the most recent, Caligula (Sceptre), which I think will be the last, was published only in November. During this time I have practised self-denial, declining to read any novel set in the same period, for fear of being influenced by it.

There have been a great many such novels. The most recent, also a huge success, was Robert Harris's Pompeii, itself reported to be the first of a series and likely to be filmed, something already happening to Ross Leckie's Hannibal. The fashion for setting crime novels in the past has spread to ancient Rome, where Lindsay Davis, David Wishart and the American Steven Saylor are setting the pace.

So what is the attraction for the novelist - and, of course, for the reader, without whom no Roman novels would be written, or at least none published? It can't be novelty. People have been using Roman settings almost as long as novels have been written.

Bulwer-Lytton published The Last Days of Pompeii in 1834. Ben Hur, by the American Civil War general Lew Wallace, dates from 1880; Quo Vadis, by the Pole Henryk Sienkiewicz, from 1896. Robert Graves's two Claudius novels are now almost 70 years old; I don't think they have ever been out of print.

These titles provide some of the answers. There is first what may be called the Hollywood factor. Ancient Rome offers us drama on a grand scale; society that is colourful, turbulent-magnificent, cruel, with no half-tones, history in Technicolor, all the actors larger than life, their passions unrestrained. Howard Fast's Spartacus, filmed by Stanley Kubrick, is a perfect example. Like Ben Hur and - perhaps - Conn Iggulden's novels, it was a book crying out to be filmed.

Second, there is the attraction of the clash of civilisations: Paganism meets Christianity. Quo Vadis presents us with the contrast between the luxury, cruelty, immorality and decadence of Nero's Rome and the new hope for mankind offered by the cross. You get it both ways, invited to revel in Neronian luxury and also to be uplifted by the nobility and self-sacrifice of the early Christian martyrs. What could be more agreeable? The Robe, a post-war bestseller by the American Lloyd C Douglas, exploited this duality splendidly. It too was filmed, with Richard Burton as the Roman soldier eventually converted by the evidence of Christ's suffering on the cross. As if decadent Rome wasn't sexy enough, there is always a female lead - either slave girl or high-born maiden converted to Christianity, whose virtue is threatened, until...

It is possible, however, to write about Rome while eschewing the Hollywood touch. Some of the best Caesar novels have done this, and, though Iggulden may be correct when he says that "Julius Caesar has a fascinating life story that isn't commonly known", there have been a good many of them. For the truth is that Rome of the last century BC and the first century AD presents us with power politics at their most naked and compelling. That, for me, certainly has been its chief fascination.

In the 1930s - the decade of the dictators in Europe - novelists such as Jack Lindsay, Thornton Wilder and Rex Warner found parallels in Rome for what was happening in their own time.

Iggulden has said in an interview: "I like Julius Caesar for the same reason that Shakespeare tended to write about kings. There is something awe-inspiring about those who are so different from the mass of humanity, and their lives tend to revolve round the great issues and dwell less on the mundane."