Monarchy is distinguished from tyranny by several things in the classical tradition. One might be that monarchs are restrained, whereas tyrants are servants of appetite. I've just come across another really interesting reflection in Marcus Aurelius's meditations
Through him [Marcus's brother Severus] I came to know of Thrasea, Cato, Helvidius, Dion and Brutus, and became acquainted with the conception of a community based on equality and freedom of speech for all, and a monarchy concerned primarily to uphold the liberty of the subject.
Marcus's statement here is fascinating. Monarchy is coupled with liberty. Furthermore within the statement is an implicit rebuke to tyranny: Thrasea was executed by Nero, as was his son Helvidius. Cato died at the hands of Caesar. Brutus could refer either to Lucius Brutus- who slew Tarquin- or Marcus Brutus- who slew Caesar himself and died at the hands of Octavian. These are emblems not just of good citizenship in a republic- indeed none of them lived under a republic (if you agree with Harriet Flowers' account of the Roman state)- they were emblems of rebellion. Its as though Prince William were to sign off a letter about the liberty under a crown by saying that he believed in the ideal of liberty under monarchy as preached by Cromwell and Tom Paine.
How could Marcus say this? In part I think its because he shared a philosophical attitude with these men- throughout his meditations he stresses the importance of standing up for one's own beliefs and opinions- being true to onesself in the ghastly modern phrase. Marcus means something more by this than we might- in the sense that he sees every single human reason as an expression of divine reason. In part I think its because the contrast he draws here is between one type of 'bad' monarchy and another more legitimate 'good' monarchy: because Rome's system was not hereditary, Marcus is not involved in the fate of Nero or Caesar in the same way as Victoria was in the fate of Charles. His belief system brings together these two conceptions- the first of self control and the second of good monarchy- I think through something else- which is the image of a good statesman. Curiously enough a rebellious subject may become the emblem of a good statesman in Marcus's world- so Brutus looks more like a monarch than does Nero. If that's true then lauding these individuals for their steadfastness in the public interest becomes in a way a certificate that men can hold to the principles of good statesmanship. In that sense- the rebellious subject is the mirror image of the good monarch- the tyrant of the flattering subject.