A sergeant was attached to the UNIT force attending Space Control during the Mars Probe 7 incident. At one point, he went with the Brigadier and the Third Doctor to retrieve Recovery 7 after its splashdown in southern England. The convoy of which he was a part was beset by General Carrington's forces, which included a helicopter that was bombing the convoy with grenades. He was the last member of UNIT standing in the skirmish, and he unsuccessfully attempted to commandeer the helicopter in mid-air. (TV: The Ambassadors of Death)
Behind the scenes
Ware is only credited in episode two of the serial. However in part one of Ambassadors, he is quite clearly seen in the same uniform being beaten up by Collinson's forces. Because he's uncredited in that episode, it's unclear whether the narrative intent is that the two Ware-played UNIT soldiers are the same character.