First Cohort of the Ninth Legion

The First Cohort of the Ninth Legion was a robot that served in the Iron Legion.

He shot and killed a shopkeeper, before suffering from an apparent malfunction - unable to cope with the impossible calculation of there being two hearts in one human body (not realising that the Doctor was a Time Lord). The Doctor wasted no time in removing the robot's head with his Sonic screwdriver, and and identifying him as the First Cohort. (COMIC: Doctor Who and the Iron Legion)