An Italian prosecutor has revealed that the Mafia has been sending information to its jailed bosses through a television football show. The show runs fans’ text messages along the bottom of the screen. Unknown to its producers, mobsters used this facility to send coded messages to their associates serving maximum-security sentences.

The prosecutor remarked on how ordinary the messages seemed. One read, simply: “Everything’s OK, Paulo.” If they were not to attract suspicion, they could not be anything else. But the apparently banal secret message is desperately difficult to get right, as an intriguing book by Diego Gambetta, an Oxford University sociology professor, makes plain.

There are many dangers: that the recipient of the message might misunderstand it, or that others, such as the police, might understand it all too well. And whereas a failure of communication in the business world can result in a loss of a contract, for criminals, sending the wrong message could mean years in prison, or worse.