[ Clara looks up at him, searching his eyes and wanting to ask if he promises. She doesn't, because he promised her three times on that he wouldn't be anywhere without her, and three times he tricked her into going back to Earth while he stayed on Trenzelore. So, she doesn't say it. Instead, she huffs. ]

I'll wake up and you'll've already come back, half your memories gone. [ And no diary to shove in his face this time. ] Look, the kids are too important to wait, so at least say you'll try not to inhale too much or something. Can't you bypass something or other in there?

[ Clara gestures at his entire body. ]

You know, superior Time Lord physiology and all.