It's Classic blood and guts

But most likely you’ll have heard his name in conjunction with the bestselling Warrior of Rome, his trio (so far) of adventures set in the beleaguered eastern provinces of the Roman Empire and crammed to the 400th or even 500th page with cauldrons of swash, buckle and cruel, pillaging Persians.

After top-five hits with Fire in the East (the siege of Arete, in Mesopotamia) and King of Kings (religious fanaticism and intrigue in the imperial court), last month saw the release of the trequel, Lion of the Sun, in which the emperor Valerian is betrayed while on campaign (AD 260) and the readers are reunited with the Saxon-born hero, General Ballista: cue brutal battles scenes, heroism and political skulduggery.

Lion of the Sun has already sold more than 14,000 copies.

Now it’s Friday afternoon, and we’re sitting on the terrace at Oxford’s Quod, with some fine Peronis, and turning the air Imperial purple with cigarette smoke and some of the novel’s riper dialogue.

Sidebottom, a jacket-and-jeans kind of guy, enjoys playing the regular bloke. Aside from being lecturer in Ancient history at Lincoln College and a Fellow of St Benet’s Hall, he lists his interests as “fiction, travel, sport, booze, and women [Erica Jong not included]”.

I also notice, retrospectively, that he’s ‘Dr Harry Sidebottom’ on the frontispiece of his books — but not on the dust-jacket.

The Warrior of Rome novels have garnered specific plaudits for their elaborate and detailed militaria, both in intellectual and material terms. But apart from a stint in the CCF at school (King’s, Ely), Sidebottom is not a military man.

He knew the first novel, Fire in the East, which he describes as “very army” (“I like sieges. Unity of time and place and all that”), was read in Basra — “Yeah, because a mate of mine took his free copy on deployment, and then let everyone else read it!”

But on a recent pre-publication tour of the north (Leeds, not Germania) he was particularly chuffed at the number of forces personnel who came to his events and asked about his soldiering.

His own training was originally in archaeology, at Lancaster, before he switched to Ancient history (“I didn’t want to spend my summer holiday excavating Preston”), a path of enquiry that led eventually to his PhD at Oxford.

And anything that’s not covered by that portfolio (you don’t need to have watched everything from Caligula to Generation Kill to appreciate that squaddie ‘nuance’ hasn’t developed much in 2,000 years) he makes up for with voracious fiction-reading and travel.

It is his avowed intent to visit every place he writes about — with the emphatic exception of bandit-ridden rural Georgia.

He is heavily influenced by Patrick O’Brian’s sea stories. And he draws structural support from Tacitus (“the best historical writer ever was basically a novelist”), whose Annals, also, were organised, thematically, in clusters of three.

Sidebottom quickly rattles off all of his 12 planned titles in the series, along with their basic themes. Volumes one to three in the Middle East; four to six around the Black Sea; North Africa to feature later.

“It’s a big cast, and there’s space for characters to develop, to come and go, get old and fat and disillusioned. I don’t want to give anything away; but let’s say that some of the main characters probably don’t make it to the end.”

Volume four will be out next July, he says.

How did a historian of classical art and warfare come to be writing novels at all?

“Well, we were drinking in the pub and my agent said, ‘Why don’t you take eight weeks off and write a novel?’. So, I produced a synopsis and three chapters. And I sent my agent one manuscript, and he sent it to one publisher, Penguin. There’s none of that ‘I starved in a garret’ stuff.”

(He refers to a “life-changing sum of money”. Given Sidebottom’s flourishing readership and current commercial momentum, you’d have to say Penguin got that call about right.) Sidebottom is proud of his sales and the popularity of the whole sword-and-sandal business (“Yup, Gladiator restarted it all.”).

But like the teacher he is, he can’t help enthusing about the facts behind the fictions.

“There’s clearly an appetite for heavily textured fiction covering everything from Zoroastrianism to Epicureanism via table manners in Rome.

“It shows even the mass-market reader doesn’t just want Andy McNab in a toga.”

The non-facts, too.

Censorinus, his spy chief, for instance, was real — “or a real fake, anyway”, derived from the bogus Augustan History (c.400 AD).

“The author invented guys who were never emperors. Like Ballista.”

“Your Ballista? Or a different guy with the same name?”

“Or a different guy with a different name.”

“Right...”

“There are four things [included in Lion of the Sun] he may have actually done. Or not. Maybe someone else did them for him.”

The great crisis of the third century is “very chaotic. Full of gaps”, a whole stretch of Roman history not even covered by the undergrad Classics syllabus.

It is also Sidebottom’s academic stock-in-trade.

“I was very much drawn to it because it allows a certain freedom to the novelist.”

Or, as one colleague put it: “Congratulations, mate. You’ve chosen a period where no one can prove you wrong.”

(Though there was the small item of a retired Australian general who wrote to point out that eucalyptus was not, ahem, widely available in Mesopotamia at that time.) Not that it matters. “The novels aren’t history books in disguise. I’m not writing them as an outreach programme.”

So how has Warrior of Rome been received by his academic peers?

“At the outset, the only professional historian I told was Mary Beard.”

But every Classicist he’s talked to since has been very positive.

“I think they realise if we don’t reach out to the broadest possible audience the subject they love will die.”