1973 stage play by Alan Ayckbourn; first part of The Norman Conquests trilogy (5,7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
table manners
(Other definitions for table manners that I've seen before include "Good eating behaviour" , "Behaviour at meals" , "A branch of etiquette" , "Meal etiquette" , "Dinner time etiquette" .)