As the Master settles down, so does the Doctor, lowering himself down and reclaiming a stable position. He leans forward, one hand on the mattress next to the Master's body, until the head of his cock just so brushes against the Master's ass. His other hand is still resting on the Master's buttock, and he begins trailing it inward, when the Master speaks up.

The Doctor stops in his tracks, his grip on the Master's ass tightening ever so slightly.

"What did I just tell you?"