He had tried to warn John, to be fair. Tried to warn him how close he is, and that it wouldn't take much to bring him that much further over the edge. John smiles at him and for a moment he thinks that means he's about to switch this up then -- and in a way he's right, although it's to intensify his attentions instead. Ianto cries out, bucking his hips forward into John's mouth with the surprise of the movement.

He fists his hand in the other man's hair again and means to tug him back but in the end he just mostly ends up hanging on, grinding out the other man's name as he feels his body tightening. It's the only warning he can give before he spills over with a sudden gasp, arching back against the bed and fisting his hand in the blankets there. Doing his best not to thrust too hard into the other man's mouth though unable to help his desperate rocking completely as he finishes.