He was watching the Celtic v Blackburn game and didn't answer the door, so Gareth took a quick Polaroid of himself and pushed it through the letterbox.
10 minutes later Lisa came home from some extra maths classes to find the Polaroid on the doorstep with a message: "To Lisa, I popped in to say hello but you weren't in! Lots of love, Gareth."
Understandably Lisa wasn't happy: "I haven't got over this and I'm not going to speak to my dad for ages."