In an age of chivalry, England's tournament-loving, debt-ridden King Edward III (1312-77) took a poor view of unregulated trade. To punish merchants who went on selling their wares after a fair had officially closed, Edward's Parliament passed a law under which anyone who successfully sued a black-marketeer could collect part of the culprit's fine.
Down the centuries 42 additional acts under which private persons might bring an action and collect the fine money were passed. People who went in for this were officially called common informers.* Although branded "viperous vermin" by James I's Lord Chief Justice Sir Edward Coke,...