Going back seven years, the first tweet to direct a tweet at someone was Robert Anderson to Buzz Anderson (no relation)

(Also, note the verb “twittering” – how times change)

This wasn’t a recognised standard though – it was only when Ben Darlow suggested a pseudo-text standard that would inform a user of a tweet directed at them.

Neil Crosby was quick to respond in an appropriate manner:

Thus, the @reply was born.

It wasn’t until May 2008 – 18 months after the suggestion – that it was officially supported within the application although there was unofficial support through third party tools and services beforehand.