Lustrum, By Robert Harris

Lustrum is one of those intriguingly Janus-faced words. As the definition that serves as one of Robert Harris's epigraphs explains, it means at once "a lair" or "debauchery", but it is also the name of a sacrifice of expiation. As Harris's novel repeatedly demonstrates, those required to purge viciousness from the state often become the source of further danger themselves. Lustrum also denotes a period of five years, and this book covers a frantic half-decade in the career of Cicero. The second of a trilogy about the life of the great orator, it begins as he is about to become consul, the highest office of the Roman state. Cicero was very much his own man: from a humble background, he married cannily and climbed the greasy pole because of his brilliant legal mind and political acumen. But in power, he finds his ability to accomplish anything thwarted by entrenched interests. More dangerously, Catalina, Cicero's defeated opponent, plots against the republic and the life of the consul himself.

The parallels with the War on Terror, which began in Imperium with Pompey's war against the pirates, continue. Rome is awash with uncertainty: conspirators are suspected behind every door, even in the colonnades of power. Harris is no naïve partisan for either uncompromising libertarians or security hawks. Catalina's machinations are real enough; but, because the narrative is told entirely from the point of view of Cicero's confidential secretary, Tiro, there is an ambiguity as to whether the dissatisfied are in fact backed into a corner, radicalised by Cicero's own underhand tactics.

Harris's darker purpose has supposedly been to allegorise the career of Tony Blair. There are distinct points of intersection: Cicero in the Senate tries to chart a third way between the populists and patricians, on whose votes he relied but with whom he has no great affinity. Yet what most of the similarities make apparent is the unchanging nature of politics. It tends to be conducted by lawyers and soldiers, people make deals, renege on them, and live with the awareness that no one can maintain power indefinitely.

Harris has no qualms about cherry-picking iconic moments from political lives: there is a cheeky snapshot of Cicero as JFK, with his young daughter playing under his desk while he works.

For the most part, the unsubtle characterisation does not interfere with the hectic pace of the story. Women are shrews, hussies or entirely bland.

The male politicians are equally one-dimensional – Caesar is ruthless, Clodius lustful, Crassus avaricious, Cato a fervent idealist – though this actually gives a sense of the monomaniacal focus necessary to succeed in politics. But Cicero needs to be a more complex figure: Harris wishes him to be seen as decent but flawed, a pretty straight kind of guy who, after he thwarts Catalina's conspiracy (brutally and possibly illegally), becomes a bore, bloated with pride, banging on about the days when he saved the Republic, and writing a dire epic to his own greatness. Yet there is no serious demonstration of the way that power changes Cicero's personality.

Nonetheless, Lustrum offers great insight into the psychology of political calculation. The story of Cicero's fall from power to the point when even sworn allies close their doors on him offers little consolation over the next few months for our own leader.