Antimony (Death Comes to Time)

Antimony was an android companion of the Doctor.

Biography
Antimony was apparently constructed by the Seventh Doctor to be a permanent companion. He did not know he was an android. Ace knew of him. He was killed by Tannis after finding out what he really was. (WC: Death Comes to Time)

Behind the scenes

 * The canonicity of Death Comes to Time is uncertain, even in relation to other spin-off media, so the truth of the foregoing is debatable.
 * Antimony's appearance was modelled on that of actor Kevin Eldon by illustrator Lee Sullivan.