He's beaming at the direction things seem to be going; Ianto and the Doctor have such a nice rapport, and of course, he has other reasons to enjoy watching. It's Jack, after all.
"Hmmm...? Oh come on, he never would've-- I mean, I liked that he flirted back sometimes and all, but he only had eyes for you then. ... Didn't he?" He furrows his brow and applies that ol' imagination. "... Oh my god, seriously? Damn it! I wanted him!"
He grins broadly at where her thoughts are going. "I'll be no good at not letting Ianto in on it, sees right through me, but he's fantastic at keeping a straight face. I could send him a little text if we-- Wait! They're on the move!"
It doesn't take long to realize why. "Right, under my desk, they're coming up for coffee. We need more time and they need more time!"