People use their mobile phones all the time: when they are not announcing to their other half that they are "on the train", they are madly contributing to the millions of text messages sent each month. At least, that is the theory. In practice, Vodafone, the world's largest mobile phone group, says people use their phones for just four minutes a day on average and send less than one text message every 24 hours.

Not enough, says the UK-based network operator, which sees its growth running into the sand unless it can find ways of persuading its customers to make more and better use of their phones.