Coot, gripped by rude urge, not behaving in line with convention (2,7)
I believe the answer is:
de rigueur
I'm afraid I can't explain this answer.
Can you help me to learn more?
(Other definitions for de rigueur that I've seen before include "Required by etiquette, as in France" , "Obligatory" , "Required by custom or etiquette" , "necessary" , "Proper" .)