Sorry, NCIS reference - it's a sharp slap to the back of the head, you never see it coming, but it sure wakes you up and gets your attention!

Gwen was always too busy juggling living with Rhys, shagging Owen and mooning over Jack to notice Ianto (or Tosh) that much, I think to her they were just sort of there, useful at times but not important enough to waste her attention on.