So, hypothetically speaking, lets say you've been out with a friend for a pizza just before you go and see the latest Star Wars film. It's almost time for the film to get going, you're collecting up the remains of the pizza, and you're paying by your debit card. It's England, so you're not allowed to add service charges onto that payment. The waitress has been kind, efficent and even bought refills over without being asked. To your horror, you suddenly discover the only actual cash you have on you or your friend is a single solitary ten pence piece.
Is it ruder to leave just that single coin and thus imply she was only worth that much, or should you slink out without leaving a tip, feeling incredibly guilty?