Ken is the former Grumman technician and former clerk in the Lunar Receiving Lab who was trotted out by Richard Hoagland at the notoriously underattended "press conference" at the National Press Club on 29th October 2007 (video).
Ken's job at the LRL was to ship moonrocks to scientists who had successfully applied to conduct experiments on them, along with context photographs showing their original environment and exact orientation. As such he had in his file cabinets a collection of copies of photo prints from the main Apollo archive, which was in a separate building.
Somehow Johnston's role in Apollo became inflated in the tiny minds of Hoagland & Bara to "Director of Apollo Photo Archives" and the reason he was introduced (to almost nobody) at the 2007 press conference was that Hoagland was convinced that Johnston was the sole possessor of incriminating Apollo photography which showed unequivocal evidence of a lunar civilization. As it turned out, the so-called evidence was not merely equivocal but downright unconvincing (compare the actual file images AS14-66-9301 and AS14-66-9279.)
Nor was that all. James Oberg found time to look into the curriculum vitae ascribed to Johnston by Hoagland & Bara and found it largely fictional. Mike Bara made a valiant attempt at defending it on the Dark Mission blog, but Hoagland, Bara, and their ignorant publisher Adam Parfrey all had to climb down and amend the text of Dark Mission's second edition. Pity they didn't correct more of the errors while they were at it.
Just over a week ago, somebody using the pseudonym LiveForever8 posted two Youtube videos (originally from Sacred Mysteries Productions) of Ken Johnston on Above Top Secret, and the controversy gained a second life. The thread makes a good read, with Oberg in fine form giving us all a lesson in how to stick to the topic in the face of many attempts to derail the discussion into irrelevance.