Charles Boyle, aka "Robinson" of Robinson and The Overcoat (see below), says in a blog post: "Careers and livelihoods depend upon just the right degree of non-seriousness. It’s a British code."
Well yes. But it's also a French code. Go to a dinner party and wax serious and pretty soon people are looking at you funny, as if you'd forgotten the rules of conversation. Oops, time to talk to the person on the other side.
In the US on the other hand, irony doesn't always go down well. Better to know the company you are in before you ironise and your neighbours take it at face value.
Canada is somewhere in between... .