Notorious murderer John Walsh repeatedly ploughed a sandwich press into his cellmate's head because he thought he had the look of a man who was planning something.

"He just died, it was so easy," the 79-year-old told police after he murdered fellow convicted killer, Frank Townsend, in their Long Bay prison cell in early January 2017.

John Walsh is taken from NSW Supreme Court in Sydney on Friday Credit:AAP

"I stepped forward with both hands and choom, onto his face.

"I don't work in anger, I work in tactical ... cold rage."