It sounds like the set-up to a bad gag: what do David Einhorn, the poker-playing activist hedge fund manager; Mark Carney, the incoming governor of the Bank of England; and the Reverend Jesse Jackson, the American civil rights leader, have in common?

The punch line (which is definitely not funny): they all want to get their hands on the record cash piles sitting "idle" (we'll discuss just how idle in a minute) on company balance sheets.