Jeff Johnson

Private  Jeff Johnson was a UNIT soldier who served under Brigadier Lethbridge-Stewart. He detected the Third Doctor's distress signal from Reegan's hideout. (TV: The Ambassadors of Death)

He and Liz Shaw went out together for a while. However, he left soon after the events involving Mars Probe 7 and became part of the regular army. (PROSE: The Scales of Injustice)

Behind the scenes

 * Johnson's first name was not given on-screen, only in PROSE: The Scales of Injustice.
 * Johnson's relationship with Liz is likely a reference to the fact that Geoffrey Beevers was the real life husband of Caroline John.