Imagine for a moment that you are a banker, who stumbles across a juicy new instrument called the "lemming" product that your sales team could sell to retail clients - for a fat profit. This product, however, looks risky, even though it has been rubber-stamped by your compliance department, since investors will suffer big losses if stock markets fall more than 30 per cent.

Would you go ahead and approve the sale of lemmings - even if investors did not understand the risk? Or would you dig in your heels, and insist that the lemming structure was reviewed - or carried a high-profile health warning?