Human beings have a remarkable facility for self-delusion, according to Nobel prize-winning psychologist Daniel Kahneman. The ability to convince yourself of something that is to your advantage but for which this is little or no evidence can be a great asset, he argues.

And it seems to be an asset with which investment bankers are particularly well endowed. Consider the question of whether changes in exchange rates affect the amount of cross-border M&A. If sterling falls against the dollar, for example, would that lead to more US companies buying British ones?