These events were one of the world's great tragedies. Tens of thousands of people died violent deaths, or had their lives comprehensively ruined, in order to turn the Rome of Cicero into the Rome of Caligula. We know how it happened, more or less; but why did it happen? Was it all down to Julius Caesar, as Josiah Osgood's and Philip Matyszak's titles seem to imply? After all, Brutus said Julius Caesar was ambitious, and Brutus was an honourable man. But that takes us back to Greg Woolf's subject. Who was Brutus, to act in the name of the Republic?

The Republic belonged to the Roman People. The Senate was only an advisory body - but recently it had arrogated to itself the right to decide which forms of political activity were acceptable and which were not. Three times in the previous ninety years it had had murdered elected Tribunes of the People for pursuing policies of which it disapproved. In 49 bc, it threatened to do so again, when two Tribunes tried to insist that Caesar be allowed to stand for the Consulship at the end of his Gallic command. That was when Caesar crossed the Rubicon, to "defend the People's liberty, and his own, from oppression by a faction of a few men". He achieved that by civil war, and when it was over the free People voted him the Dictatorship for life. But the few men were still there, and still believed they had the right to decide.

Caesar had disbanded his bodyguard. "If anything happens to me, there will be civil war again, but worse." Four years later, when the cities of Perusia, Nursia and Sentinum were smoking ruins, the historian Sallust chose as his subject an episode from two generations back, "when the first challenge was offered to the arrogance of the aristocracy, a conflict that reached such a level of madness that civil strife ended in open war and the devastation of Italy". Was that just Caesar's legacy? Or will the verdict of history also condemn his enemies, who thought they knew better than the Roman People?