Another version is: ‘Don’t overrun the constable.’ This has nothing to do with not running faster than a policeman, or shooting past him when he is on point duty. It means: ‘Don’t get into debt.’ In olden days police constables acted as debt-collectors. For example, if a tradesman allowed his customers one month’s credit, and a customer failed to pay at the end of that period, the tradesman might call in the constable, and the debtor might well be sent to prison. So, ‘to outrun the constable’ was to go beyond the point when you were safe from the arm of the law.
