Restaurant etiquette is one of the biggest Anglo-French cultural divides. In my experience, Rule Number 1 in London is: The Customer May be an Awkward So-and-So but is Paying so Give Them What They Want while Rule Number One in Paris has to be: Just Order What is on The Menu.
The flipside of British Rule Number One is that customers can get away with being difficult. They can say: "May I have the Anchovy Pizza without the anchovies?" or "Would it be possible to have a salad without any green stuff?" and the restaurant (unless it is Gordon Ramsay or Marco Pierre White who may well tell you where to get off) will do its best to produce what has been requested. So it comes as a shock to British diners, clutching wads of euros or waving credit cards, that in Paris restaurants they are handed La Carte and all but told to take it or leave it. Even if it would be theoretically possible for the chef not to put a raw egg on top of the pizza that comes with a raw egg on top or to replace the French beans with French fries or visa versa, they are disinclined to do so. La Carte has been carved in stone and could have been produced by Moses.
This is not as unreasonable as it sounds, given that most French restaurants and bistros are chronically under-staffed. I try to head off potential problems by explaining this to visitors before we sit down to eat. Sometimes my advice falls on deaf ears. Once a visiting relative ordered two fried eggs. I looked at the menu. No fried eggs. She reckoned that a restaurant that could rustle up an omelette clearly had a) eggs and b) a frying pan. The waiter looked at her as if she was green and had beamed in from faraway planet. She said: "What's the problem? They have eggs why can't they just fry them?" I said: "It's not that they can't do it. It's that they won't." She said: "But I'll pay." I said: "He doesn't care. He won't do it."
As both waiter and customer stared at each other with utter incomprehension I felt I was witnessing a minor clash of civilisations.