After having a "bit of trouble" with self checkouts (resulting in me shouting "STICK YOUR BAGGING AREA UP YOUR ARSE" at one in Sainsburys) and taking my items off it and going to a human, I can confirm they're on to you like a tramp on a bag of chips; I had a superviosor and security man come up...
A few years back I worked with a bloke, Mark, and one afternoon he said to the boss "I'm just off to get my hair cut".
The boss said "In work time ??"
Mark, "Yes, it grows in works time"
Boss "It doesn't only grow in works time"
Mark " I know, but I'm not having it all cut off"