Why Every Classic Companion Left Doctor Who
17. John Levene - Sergeant Benton
John Levene made his debut as Corporal Benton in The Invasion, but like Nick Courtney had also appeared in The Web of Fear - as a Yeti! When Benton was given a promotion to Sergeant in The Ambassadors of Death, Levene became another vital member of the beloved UNIT family who assisted the Third Doctor during his exile.
However, as the Third Doctor's adventures became less Earthbound, Benton and the wider UNIT family were gradually phased out. When Philip Hinchcliffe and Robert Holmes took over the show in 1975, the decision was made to uproot the Doctor, making Tom Baker's incarnation more of a wanderer.
The UNIT family were finally phased out in 1976, when John Levene departed Doctor Who with The Android Invasion.