Our clients’ interests always come first, declared Lloyd Blankfein, the chief executive of Goldman Sachs as he sought to overhaul the investment bank’s culture after the financial crisis. He meant, of course, that they should come before the interests of Goldman Sachs or its staff.

You can see why he wanted to stress the primacy of clients’ interest after some of the banks’ employees had been caught ripping off customers they referred to as “muppets”. But there is a problem with having this as the first of the 14 business principles Goldman Sachs wants its staff to live by. What if it is in the client’s interest, or at least what the client thinks is its interest, to act unethically?