For the past two decades, Ms Stone thinks, many people have felt overwhelmed and anxious, constantly afraid that they could miss out on social opportunities if they concentrate on any one thing.

ECONOMIST: What sort of revolution?

Yet Daniel Bouton, SocGen's boss, thinks that the two banks have too many overlapping branches to make such returns possible: in regulated France, you cannot simply close branches and sack people, which is, in part, how banks in America and Britain have increased returns.

ECONOMIST: French banking