My son works at a restaurant where some of the travelling chaps have on a couple of occasions ordered a rare steak amongst a large order, then refused to pay the entire bill, including drinks on the basis that the steak was under cooked and that ruined the meal for all eight of them.
This is the reason for those annoying check backs that waiting staff do, "is everything alright for you?" which always seem to be whilst you have a mouth full of food or before you have even stuck a fork in it.
Same happened when a friends daughter was working in a local very good Indian Restaurant, a couple of pikeys and their toddler, woofed down the food and what a mess there was around their table disgusting, then they screamed and shouted saying a cockroach was in their food and started telling the other diners.
When it was pointed out to a few other diners that this was unlikely and have a think who these people were there was a bit of a kerfuffle and they left without paying.
Lovely stuff........