Jack looks at him, hurt and sad beyond measure that it's all come to this. It was only yesterday, it seems, that they were so happy together, so in love, even after Spike came on the scene. How could Ianto think he was just convenient? He knew what a mess Jack had been after he'd died - both times - and how much he'd been prepared to go through to keep hold of him.
"Well. If that's really what you think of me, I guess we really don't have anything more to say to each other," he says coldly, because he doesn't think he can bear to go through this yet again.
He even turns to walk away, but he only gets a couple of steps before he swings back again to add viciously, "After all, you've got what you wanted now, haven't you? A doting, sickeningly romantic boyfriend who's prepared to stick with you and only you for eternity? What would you ever need with me?"