George Patrick Barnham was an inmate of Stangmoor Prison.
George Patrick Barnham (TV: The Mind of Evil) was a thief. Whilst robbing a safe, he was caught by a security guard and choked him to death. He was arrested and throttled a fellow prisoner over a cigarette before half-strangling a prison officer. (PROSE: The Mind of Evil)
He was subjected to the Keller Machine, which extracted all the negative impulses from his brain. Due to this, his presence acted as a dampener on the machine — i.e. it would not function while he was present.
Working with the Third Doctor and Jo Grant, Barnham brought the machine to the site of the Thunderbolt rocket, which incapacitated the Master and allowed the Doctor to fix the missile's abort mechanism and stop its launch. He sat near the machine, allowing the Master to escape in a police van. During his escape, the Master ran over Barnham, killing him. (TV: The Mind of Evil)