This week marks the 30th anniversary of the reported first use of the "emoticon", the keyboard characters used in text and other messages to denote a smiley face.

Sam Leith, a writer on online trends, explained that emoticons began as a way of "disambiguating" what was said online.

He told the Today programme that they started out as having a purpose but now "they've spread like knotweed".

"Sparingly is the way to use them," he advised.

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