"I'll do my best, but the more I care, the more he's likely to actually try to do so, just to irritate me." The Doctor gave the Master an annoyed look. "As for you? If you don't behave, I'll go find your former regeneration - and every other variation of you I can - and hand you over to them. I'm sure they can be quite creative, without forcing you to regenerate."
He paused, processing Jack's words, and rolling his eyes. "Did you have to kill Jack, again?"