"Exactly." You've been listening. The Doctor is almost impressed.

He can tell that the Master is waiting for him to hit him again--the way the other man goes entirely still, entirely relaxed under his fingers is clue enough; he does know the Master pretty well--so he doesn't. He simply runs his hand over the smooth skin of the Master's ass, down along his side and to the back of his thighs, and tilts his hips forward, his cock once more nudging against the Master, with more pressure this time. He waits until he feels the Master tense with disappointed anticipation, and then raises his hand and hits him again, harder than before.

He leans in close, bringing his mouth close to the Master's ear. "Then do so."