Toberman

Toberman was Kaftan's servant. He accompanied her on Professor Parry's expedition to Telos. He was captured by the Cybermen, partially cyberconverted, and placed under their control. When the Cyber-Controller killed Kaftan, Toberman regained his humanity and attacked the Controller. He sacrificed his life to close the electrified doors of the Cyber-tombs, sealing the Cybermen in. (TV: The Tomb of the Cybermen)

Behind the scenes
Toberman was intended to be deaf, but there appears to be no reference to this in the episode. However, the reference did make it into the novelisation.