In "The Power of Three", UNIT is shown to have a scientific research department with a large laboratory in the base beneath the Tower of London.
During the story, the laboratory is dedicated to studying cubes that appeared out of nowhere.
Sherwin was uncertain if the army forces featured in The Web of Fear appeared as UNIT, but was "convinced" that, as a teaser for UNIT's more substantial role in The Invasion, The Web of Fear was supposed to have replaced the basic army forces that were seen in the story.
On top of this, production notes in Doctor Who: The Complete History credit Haisman and Lincoln as the owners of Lethbridge-Stewart, who was the army leader from The Web of Fear, and mention how Bryant and director Douglas Camfield were negotiating the use of the character for The Invasion from Haisman and Lincoln in May 1968, the same month the serial was commissioned.
Speaking in an interview on the 2011 special edition DVD of Spearhead from Space, Sherwin claimed that he had created UNIT because he wanted to give some "considerable support" to the Doctor, "so that [Troughton] didn't have so many damn lines to learn each week".
The final appearance of UNIT during the original run of Doctor Who was the Seventh Doctor serial, Battlefield (1989).
In "The Power of Three" (2012), Kate heads UNIT's scientific research department, which now has authority over the military branch.
the British troops of UNIT are armed with standard British Army weapons such as the L1A1 Self Loading Rifle, Sterling submachine gun, Browning Hi-Power pistol and wear 58 pattern webbing.
In a 2014 interview with Doctor Who Magazine, script editor Terrance Dicks recalled that he was present at the "birth" of UNIT during the production of the Doctor Who serial The Invasion (1968).
He credited both scriptwriter and script editor Derrick Sherwin and producer Peter Bryant as having come up with the idea beforehand, claiming that they were testing the concept in The Invasion before it had become central to the show in the Doctor Who serial Spearhead from Space (1970).
UNIT's personnel have a wide range of weaponry to call on, some custom-made to combat specific threats.