When one M&A lawyer walked into a pitch recently, empty coffee cups had been left out. It obviously suggested his client faced competition because another presentation had just taken place, but perhaps all was not as it seemed.

"People try all kind of tricks," said the lawyer. "If we're going in for a pitch, you can guarantee people will leave sheets on the table to make it look like they have six other presentations. They leave empty coffee cups to make it look like someone else has been there. We put up with all kinds of rubbish in this job."