Citizen K by Mark Singer is the authorized biography of Brett Kimberlin. This appears on p. 184.
At Oxford, he [Kimberlin] was assigned as a quality-control clerk at the prison factory that manufactured cables for military aircraft and tanks. His task was to inspect the finished goods. Each day, he said, he did his work quickly and then tried to immerse himself in a book, but the prison guard who was his overseer objected to his reading on the job. When he persisted, the guard threatened to give him a “shot”—to write an incident report that could lead to disciplinary action. So he stopped bringing a book to work, he said, and instead devoted his spare time to sabotage. “I’d run the cables through quality control,” he said. “I’d check them. I’d sign them off. And then I’d cut some of the damn wires.”