I can compare this to when I was a teacher. If a parent had come to see me at the start of the year, and said his daughter was not very bright and rather lazy, but they were looking to me to get her through her GCSE, I should have smiled sweetly and and said I would do my best. If when she passed, the family had sent me a thank you card and, say, a nice bottle of wine, I should have been happy and pleased to accept it. On the other hand, if at the beginning of the year, he had come and pressed some used fivers into my hand and said, ‘Make sure she passes.’, I should have been appalled, insulted, refused the money, reported the matter to the head, and tried not to hold it against the child. Perhaps a maître d’ might feel the same.