Thief (The Power of the Cybermen)

In the 41st century, a thief stole documents from the Torchwood Archive detailing how to build a Cybus Cyberman. He then began building an army of Cybermen to sell to the highest bidder as high-tech soldiers. However, his plan backfired when the Cybermen he created turned him into a semi-converted slave, forcing him to help them grow their numbers.

Investigator Jayne Kadett tracked the thief down on Centuria, where she and the Tenth Doctor were kidnapped by the Cybermen and taken for conversion. The pair managed to escape, destroying the conversion facility and killing the thief in the process. (COMIC: The Power of the Cybermen)