Sherwin told "Doctor Who Magazine" in 2014 that while working as script editor on the "Doctor Who" serial "The Web of Fear" (1968), which also involved an army, he told scriptwriters Mervyn Haisman and Henry Lincoln to include all of the characters that he had originally invented for "The Invasion". 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. Sherwin asserted that he held the copyright on Lethbridge-Stewart, as he "created him in "The Invasion"". However, previously in an interview recorded for the 2006 DVD of "Inferno", Sherwin described "The Invasion" as the start of UNIT and the beginning of the Doctor "coming down to Earth". 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, subsequent to "The Web of Fear" being broadcast in February and March. "The Web of Fear" is also described in the notes as being a "major influence on "The Invasion"".