Segestes

From Velleius Paterculus' history of the Battle of the Teutoburg Forest:

This (Arminius' ploting) was disclosed to Varus through Segestes, a loyal man of that race and of illustrious name, who also demanded that the conspirators be put in chains. But fate now dominated the plans of Varus and had blindfolded the eyes of his mind. Indeed, it is usually the case that heaven perverts the judgment of the man whose fortune it means to reverse, and brings it to pass -and this is the wretched part of it- that that which happens by chance seems to be deserved, and accident passes over into culpability. And so Quintilius refused to believe the story, and insisted upon judging the apparent friendship of the Germans toward him by the standard of his merit. And, after this first warning, there was no time left for a second.