Jack sucks in a little breath at the decision and he gives Ianto a blinding smile. "Been a while since I last tried that!" he admits breathlessly, fingers tightening again on Ianto's arm, his other hand dropping to Ianto's shoulder. If this hadn't felt quite so intense, he might have put his hands behind his back, show of submission and so on, but he doesn't quite trust himself to balance without hanging onto Ianto. They're well away from his own body, though, so he thinks this'll do. And it'll let Ianto feel every tiny clench of his hands whenever he thinks Ianto's going to press that button and send those vibrations up another notch.