The Doctor was expecting the Master to call this off--he could tell that the Master wasn't comfortable with this, and was getting less comfortable with it by the moment--but he wasn't expecting to be physically attacked. The Master's foot hits him in the chest, and he loses his balance, pulling part of the covers with him as he unsuccessfully tries to keep himself from falling off the bed.

He lands on his back, and there's a moment of breathlessness as the impact stops him from drawing in the air that the kick knocked out of him. Then there's the Master, putting more pressure on his chest as he leans on him with one hand, his other closing around the Doctor's throat.

The Doctor's reaction is instinctive. He jerks his legs up and out, trying to shake the Master off. His right knee only brushes against the side of the Master's leg, but his left hits soft tissue. The Master makes a choked sound, and his grip on the Doctor loosens enough so the Doctor can push him off easily. He rolls out from under him and to his feet in one quick motion, then turns around to see the Master lying curled up on the floor, his hands between his legs.

The Doctor takes a couple of deep breaths. "As you wish."

He quickly gathers up his shirt and trousers and leaves the bedroom, slamming the door shut behind him. He needs a moment. He's sure the Master does, too.