In July 1966, he was approached at immigration desk number 5 by the Second Doctor and Jamie McCrimmon, where they told him that they had discovered a dead body, Gascoigne's body. He was quite patronising to them, and said that they could find a policeman in the main concourse, but they needed to show him their passports, which they didn't have.
When Jamie mentioned the TARDIS, this raised Jenkins' suspicions, and he called the Commandant, believing that he had two of the suspects who ran from the TARDIS on the runway. Later, when the Commandant decided to have a look with the Doctor and Jamie at the Chameleon Tours hanger, he told Jenkins to tell air traffic control where he was.
Later, Inspector Crossland questioned Jenkins, asking him whether he had seen his colleague, Gascoigne, providing him with a photograph of him. Jenkins said he did remember because he had a pass but didn't know his name and that he didn't remember seeing him returning.
Jenkins' identity was taken over by a Chameleon. Jenkins' body was discovered and the false Jenkins was killed when the armband-like device was removed from the original's arm. (TV: The Faceless Ones)