From today’s FT Letters:

In a world where interest rates had, for centuries, been positive, it’s not hard to see why a programmer would put some validation into code to check for a positive number. Even now when I read about “fat finger” errors where a trader mistakenly buys or sells a number of shares with several more zeros than expected, I wonder why there isn’t more validation (or some secondary control that routes unusual transactions to a second person for checking). BombMoscow might, of course, have needed several levels of such controls, whether a parameter or hard coded.