Gustave Lytton said that Vincent Russell was at the centre of the dissent in his team. (TV: Attack of the Cybermen [+]Loading...["Attack of the Cybermen (TV story)"])
The Time Lords noted that dissent was almost unheard of in the Dalek hierarchy, though it might occur if given orders conflicted with a Dalek's fundamental operational parameters. (PROSE: Dalek Combat Training Manual [+]Loading...["Dalek Combat Training Manual (reference book)"])