UNIT soldier (The Ambassadors of Death)

A soldier who was a member of the UNIT security detachment to the British Space Centre served as a guard at the complex' main gate. He was attacked and apparently killed by one of the aliens who was trying to break into the British Space Centre. (TV: The Ambassadors of Death)

Behind the scenes
The UNIT soldier was played by Max Faulkner, who later portrayed Corporal Adams in The Android Invasion. They are unlikely to be the same character, however, since Faulkner's Ambassadors character doesn't clearly make it out of episode four alive. Faulkner is in episode six, but it appears to be a production error. He goes uncredited in part six, and the scene appears to have been edited in from work actually meant for episode four. The very clear narrative intent of part four is that he was killed by the ambassador. Indeed, INFO: The Ambassadors of Death says that the script does actually indicate the soldier died — but that the manner of death is very different than what Michael Ferguson shot.