HAD IT BEEN TACKLED BY ALMOST anyone else, turning the life of a 1st-century BC Roman politician into blockbuster fiction would surely have been considered an impossible mission. But, having seen just one chapter of Imperium, Robert Harris’s publishers in Britain, America and Germany urged him to continue. So it is that the 49-year-old author of four bestselling historical thrillers, three set in the 20th century, returns, roughly speaking, to the world of his previous novel, Pompeii.

The 400 pages of Imperium break into two halves, the first dominated by a great courtroom drama, the second by a tight electoral race. Harris intends it to be the first of three novels about the life of Cicero, the great orator who lived from 106-43BC. Imperium is not a thriller — unless you find courts and elections thrilling. It is verbal rather than visual, so will not quicken pulses at movie studios. It is low on violence, short on sex and highly faithful to the known facts. It is, in short, the antithesis of the BBC/HBO’s glossy toga-romp Rome (which Harris hated). As he talks about the novel, I grow convinced that he is prouder of this than of anything he has yet done.

“I feel this book is much more personal to me and different to any of the others,” he says. “I’ve been able to put a lot more of myself in it. There are more of my obsessions in it. This really is the product of 35 years of interest in politics.”

The son of a Midlands printer, Harris as a teenager developed an interest in politics as anorakish as other boys’ obsessions with football or pop (as it happens, his brother-in-law is Nick Hornby, author of Fever Pitch and High Fidelity). At the age of 16, he stayed up to watch both bitter 1974 elections. It was not only the political race that fascinated him. Each autumn he would watch the BBC’s gavel-to-gavel coverage of the party conferences and take note of the oratory deployed. Some call football the beautiful game. Harris agreed with Disraeli: politics was the great game.

After graduating from Cambridge, he became a reporter on Newsnight and Panorama and politics continued to compel him. In the late 1980s he spent a short, unhappy spell as The Observer’s political editor (during which the paper’s internal politics defeated him). He resigned and, a few months later, submitted to his agent the beginning of a what-if thriller set in a Nazi version of 1960s Germany. Although he joined The Sunday Times as a political columnist and later transferred to The Daily Telegraph, that 1992 novel Fatherland ensured that from then on Harris would be better known as a novelist than a journalist. Imperium marks his return to his old beat.

“My aim in writing the book and setting it in Rome is to write a universal book about politics. I think that politics is, like football, a universal game. Whether it is played in an African village or a sophisticated European capital, wherever you go, the basic rules are the same.”

Rome was not his first choice of location, but he was determined from the start to resist writing a Trollopean saga about new Labour. Although he was once reasonably close to Tony Blair and remains a friend of Peter Mandelson and therefore knows the turf, he thinks such a novel would be trivial, with readers and critics interested only in working out who everyone “really” was. Instead he wanted to write a dystopia in which the Walt Disney Corporation took over the world. After 18 months, he shook his head and realised that Disney was beyond satire.

“Having struggled to write this novel, I had to abandon it and happened to come across a cutting about new evidence on the destruction of Pompeii. I said to my wife, Gill: ‘What if I did this instead?’ Since I had decided that Utopia under threat was to be my theme, perhaps this was the way to do it. I almost immediately dismissed it from my mind, but it nagged away at me and I went down to Pompeii and hit on the idea of writing about an engineer and this aqueduct. It was conceived very much as an allegory.”

Published in 2003, Pompeii was a huge seller. It read partly as thriller, partly as whodunnit. For some the eruption of Vesuvius read as a parable for 9/11. In fact, Harris was thinking of climate change (and wondering heretically if, just as the Romans superstitiously blamed themselves for the Vesuvius catastrophe, the West is not unnecessarily flagellating itself now). By the time he had finished, he was thoroughly immersed in the affairs of the Roman Republic. Telling the story of Cicero, a familiar name but no more than that to most readers, might be the way to tackle the great political novel he yearned to write.

“I did two years’ full-time research. I wanted to know the Roman Senate at that time as well as I would the House of Commons or the American Senate chamber. When I came in the door I would want to know who was sitting where: not just the normal blank rows of white-togaed figures, but who these guys were, what their history was, how they voted, what deals were done and so on. I really wanted to write a Roman political procedural.”

I suggest Imperium resembles nothing so much as The West Wing.

“It’s West Wing on the Tiber,” he agrees. “And there were two brilliant moments in the research. In two books, out of the hundreds I must have read, I saw a reference first to the fact that the ordinary 300 or 400 backbenchers in the Senate were called the pedarii, the people who voted with their feet, shuffling from one side to another.

“The second thing was this place called the senaculum, the little Senate, which was an area just outside the Senate where they used to gather until there was a quorum, so they were standing around there for an hour or more and that was where all the horse trading and the back slapping and the fixing was done. Those are just two wonderfully modern images which reinforced this sense that politics doesn’t change. It was all there 2,000 years ago.”

Explore Books

• Book Extracts

• Book Reviews

• Books Group

• Audio Books

Times Recommends

• The 100 Best Books of the Decade
• The Times picks the 50 best paperbacks of 2009
• The conversation: James Ellroy