Chisholm

Chisholm was the chief engineer of the GSO drilling project. He originally managed to escape the base when the Cybermats attacked, but was later bitten when he returned to the base with the Doctor and Amy. He was at least partially converted into a Cyberslave by the time the Doctor had perfected an antidote to the Cybermat nano-virus. He later saved the Doctor and Amy by using an amputated Cyber-Arm to shoot three Cybermen who were advancing on them.