"Sam Vimes once arrested me for treason,” said Vetinari calmly. “And Sam Vimes once arrested a dragon. Sam Vimes stopped a war between nations by arresting two high commands. He’s an arresting fellow, Sam Vimes. Sam Vimes killed a werewolf with his bare hands, and carries law with him, like a lamp—”
“Where did all that come from?”
“Watchmen across half the continent will say that Sam Vimes is as straight as an arrow, can’t be corrupted, won’t be turned, never took a bribe."