Will Hoffman

Will Hoffman was a lieutenant in UNIT who travelled with the Sixth Doctor.

Biography
On his first day at UNIT, Hoffman met the Doctor. After helping the Doctor banish an alien parasite known as the Darkness, the Doctor took Hoffman and his commanding officer Chaudhry back to UNIT HQ in his TARDIS. (ST: The Terror of the Darkness)

The Doctor took Hoffman and Chaudhry on several detours before they got back to UNIT HQ. On one of their adventures they witnessed the birth of Edward Grainger's son, John Grainger. (ST: Incongruous Details)