Theory:Doctor Who television discontinuity and plot holes/The Horns of Nimon


 * The actor playing Soldeed breaks character and starts to laugh during his death scene.
 * He seems to have a rather light-hearted approach to evil( i.e., when he says, "Goodbye, Doctor!" after seemingly dispatching him), so it wouldn't be completely out of character to start laughing at this moment.''
 * He also seemed to worship the Nimon with an almost fanatical devotion rather than just seeing them as the means to an end of a new empire, so for him to learn that everything he'd sank so much time and devotion into was a lie concocted by an alien race seeking to take advantage of him and destroy his planet, it'd be fairly reasonable (in my opinion) for him to snap and start behaving in the manner that he does during his final scene.