When Ian Chesterton escaped from the guards, he doubled back to the TARDIS. The commander put him back on guard, but Ian overpowered him. Ian took the guard's gun and made him take him to Governor Lobos' office. When they got to the office, Chesterton revived the Doctor, but were recaptured by the commander.
He was later sent to the barracks to investigate a radio loss, and when the Xeron revolution started, he tried to get back to Lobos' office, but he and another guard were shot and killed by the rebels. (TV: The Space Museum)