The Royal Shakespeare Company’s latest production in the West End is a retelling of one of the most pivotal moments in Roman, indeed world, history. It is not, though, one of Shakespeare’s Roman histories. It is Imperium based on Robert Harris’s trilogy covering the tumultuous period that saw the fall of the republic, the assassination of Julius Caesar, the establishment of a military dictatorship and eventually an imperial dynasty. The promise of momentous events is onstage before the action even begins. Anthony Ward’s design features a steep flight of senatorial steps, a vast bronze globe hangs above and a pair of mosaic watchful eyes staring from the back of the stage. Paul Englishby’s music repeats menacingly, building tension.

At the heart of the play is the concept of imperium. This was the power that the state would hand an individual, whether that was to a general leading an army or to a consul, voted in for a year’s term of office. Cicero, Harris’s central character, is a consul as the play begins. He is at the height of his powers in the Republic’s highest elected public office. It is the Republic and its rule of law that he seeks to defend throughout, his raison d’etre – something he holds dearer than his own family.

Richard McCabe is simply magnificent as Cicero. He reveals him as a complex man, not just a brilliant mind, a great orator, statesman and “Father of the Nation” but flawed, too. He never tires of tracing his meteoric rise from comparatively humble beginnings. He is a cunning political manipulator. He makes mistakes, some of them serious misjudgements. He can be vain and towards the end, those who know him best are quick to divert him from retelling yet another story about himself. One of those who knows him best is Tiro, his secretary. Tiro has written his master’s biography and we learn about Cicero through his eyes. Played by the engaging Joseph Kloska, he is Fool to Cicero’s Lear, wincing at the great man’s folly as the play goes on.

Did I say play? We’re actually talking plays here: the first, “Conspirator” and the second “Dictator”. Together they run to around seven hours. You can see them on separate nights or, as I did, as a matinee and evening performance. It’s a marathon but I can promise you won’t be bored. Imperium moves at a cracking pace, starting when Cicero is consul – unlike the book that begins with his rise to fame during a celebrated court case. On one level, this is a pity as I’d have liked to hear a little more of Cicero’s silver-tongued oratory. On the other hand, you jump straight into one of the most fascinating periods of history where you already know all the main characters but see them from a very different point of view. Rather like those failed plots to kill Hitler, Cicero spares Caesar when he passes the death sentence on his co-conspirators in the Catiline uprising. As a result, Caesar’s limitless ambitions will overturn everything Cicero holds dear.

Peter de Jersey is a silky Caesar, flamboyant, disarming and ruthless. He is Cicero’s polar opposite. Instead of a belief in law and the republic, he burns with an ambition for power at any cost. He backs the raging Cataline (Joe Dixon), apoplectic after Cicero’s manoeuvres to keep him out the consulship. Joe Dixon later appears as Mark Antony, Caesar’s apologist after his assassination (and almost as angry as Cataline). He goes on to incite the mob, raise an army and set the stage for civil war with Caesar’s adopted son, Octavian (a serenely assured Oliver Johnstone). As the rule of law falls apart, looting, arson and rioting take over and Mark Antony smiles: “Welcome to Rome.”

In such a political play, there is an obvious temptation to draw parallels to today. Power grabs overturning the rule of law, perhaps? Unfortunately, the production goes in for a few cheap laughs – the most obvious being the great General Pompey being given a fake tan and a Trump bouffant. (Actually, a closer comparison would surely have been Crassus, the wealthiest man in Rome due to his real estate empire.) These, though, are quibbles. This is a great production with outstanding performances, a deep insight into human failings and resulting political tragedies – and a surprising number of laughs. A play for our times on many levels, then. All seven hours of it.

The Royal Shakespeare Company’s Imperium at Gielgud Theatre until 8 September 2018. Production images by Manuel Harlan. For more information and tickets please visit the website.