Plato, Letters 309a

Πλάτων Διονυσίῳ εὖ πράττειν.διατρίψας ἐγὼ παρʼ ὑμῖν χρόνον τοσοῦτον καὶ διοικῶν τὴν ὑμετέραν ἀρχὴν πεπιστευμένος πάντων μάλιστα, τὰς ὠφελίας ὑμῶν λαμβανόντων, τὰς διαβολὰς δυσχερεῖς οὔσας ὑπέμενον· ᾔδη γὰρ ὅτι τῶν ὠμοτέρων οὐδὲν ἐμοῦ συνεθέλοντος ὑμῖν δόξει πεπρᾶχθαι· πάντες γὰρ οἱ συμπολιτευόμενοι

Plato to Dionysius wishes well-doing. After I had spent so long a time with you and was trusted above all others in my administration of your government, while you were enjoying the benefits I was enduring the slanders, grievous as they were. For I knew that men would not believe that any of your more brutal acts were done with my consent, seeing that I have for my witnesses