Tom Osgood

Sergeant 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, having attended universities, where he studied scientific subjects, although he admitted that he was out of his depth where the Doctor and Liz Shaw were concerned. (PROSE: The Eye of the Giant)

After he was promoted to sergeant (PROSE: The Scales of Injustice), he was called in to assist in the rescue of the Doctor, Jo Grant, Sergeant Benton and Captain Yates from the heat barrier that surrounded Devil's End. With the Doctor's help, he devised a way to penetrate 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)

By 1983, Osgood and Yates had set up tiny tea-rooms just outside Reading. (PROSE: Business Unusual)

In 2001, Osgood was a civilian in his fifties. He was brought in to help UNIT and the Sixth Doctor with an alien incursion. (PROSE: The Shadow in the Glass)

Osgood was invited by the Eighth Doctor to have Christmas dinner at the Brigadier's house. (PROSE: Faithful Friends: Part 3)

Behind the scenes

Osgood's first name was never 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. In DWM 484, Steven Moffat admitted his intention when writing was for Osgood to be the daughter of Tom Osgood. However, he did not want to state this definitively in the script as to not confuse or annoy some viewers. In the audio story Power Cell, Osgood responds to the suggestion that she had an "uncle who used to run around shooting aliens" by saying "Something like that". This is consistent with both the theory that Tom Osgood is Osgood's father and with the lack of definitive confirmation.