Tom Osgood

Sgt Tom Osgood was a UNIT technical officer who served under Brigadier Lethbridge-Stewart.

Osgood joined UNIT shortly before the Third Doctor's arrival, as a corporal. He was the most technically proficient UNIT soldier. Although he admitted that he was out of his depth where the Doctor and Miss Shaw were concerned.(PROSE: The Eye of the Giant)

After he was promoted to sergeant, he was called in to assist in the rescue of the Doctor, Jo Grant, Sergeant Benton and Captain Yates. With the Doctor's help, he devised a way to get past the heat barrier surrounding Devil's End. (TV: The Dæmons)

Soon after this, Osgood became engaged to a woman named Becky, whom he met at a folk festival. (PROSE: Dancing the Code)

In his fifties, Osgood worked as a scientific advisor for UNIT. (PROSE: The Shadow in the Glass)

Behind the scenes

 * Osgood's first name was not given on-screen, only in the novel The Eye of the Giant.
 * Osgood shares the same surname as the personal assistant of the UNIT Head of Scientific Research in the early 21st century. Both also sport similar thick rimmed glasses.
 * Steven Moffat later confirmed that the two, and by extension Osgood's sister, were indeed related.