Neither "superheroes" nor "grey panthers" are characters normally thought to stalk the corridors of a discreet, top-ranking City of London law firm.

But both are descriptions that circulated internally at Freshfields Bruckhaus Deringer last year, as lawyers there struggled to overhaul their partner pension scheme in a way that was fair, mutually acceptable and legally impregnable. Grey panthers were the older partners, concerned about reform; superheroes, those retiring whom the firm was especially anxious to retain.