"I shall begin my work with the year in wich Servius Galba and Titus Vinius were consuls, the former for the second time. My choice of starting-point is determined by the fact that the preceding period of 820 years dating from the foundation of Rome has found many historians. So long as republican history was their theme, they wrote with equal eloquence of style and independence of outlook. But when the Battle of Actium had been fought and the interests of peace demanded the concentration of power in the hands of one man, this great line of classical historians came to an end. Truth, too, suffered in more ways than one.
To an understandable ignorance of policy, which now lay outside public control, was in due course added a passion for flattery, or else a hatred of autocrats. Thus neither school bottered about posterity, for the one was bitterly alienated and the other deeply commited...Adulation bears the ugly taint of subservience, but malice gives the false impression of being independent."
[Tacitus, The Histories, Penguin]