Gemini (Rise of the Cybermen)

Gemini was a secret identity used by Pete Tyler to feed information to the Preachers via broadcasts in Pete's World.

History
Pete Tyler worked for John Lumic, CEO of Cybus Industries, to gain information which he broadcast on "encrypted wavelength six five seven using binary nine." Though he believed he was broadcasting the Security Services, he was unaware that his broadcasts were received by the Preachers. The Preachers knew Gemini as a government mole who fed them information in secret broadcasts released twice a week, including the private files of John Lumic and his South American operations. (TV: The Age of Steel)

In 2007, a message from Gemini called all Preacher agents into action. It described Cybus Industries, John Lumic, the head of Cybus Industries, and his latest "upgrade" — the Cybermen. It also told how thousands of people have gone missing. This message was received via a laptop used by Ricky Smith. (WC: Tardisode 5)

Soon after, an upload from Gemini confirmed that Cybus was moving vans out of Battersea. Miss Moore reported this to Ricky. (TV: Rise of the Cybermen)

Meeting the Preachers following an attack by the Cybermen, Pete admitted that he was Gemini. (TV: The Age of Steel)

Notably, when ChatGuest1 got the help of a group of people from another universe to track down a secret password to take down Cybus Industries that that been hidden on their network of websites, one of the clues they found was a seeming ingredient called "Gemini12". (GAME: Cybus Spy)

Behind the scenes
The voice of Gemini's message in Tardisode 5 was provided by Robert Booth, who also voiced a message from Cybus Industries in Tardisode 6.