Stephen Fry meets the brains behind the mobile phone.

In this third episode, he looks at the discovery of text messaging. The engineers who designed the early texting facilities didn't imagine that anyone might want to reply. (Just in case, they added a short list of possible pre-set answers: yes, no and maybe).

In the eighties, when network coverage really was patchy, voicemail was a way of charging people even more for a service that was already hugely expensive and basically rather poor.

Before the invention of GSM, calling Estonia was the only way to pick up messages from another network. Texting triumphed when paging was all the rage, partly because paging services never seemed to work on Friday afternoon.

Produced by Anna Buckley.